Alright, according to the ratios this is one of the hardest achievements in the game, so I'll give it a shot to a guide. I did this with Frank Weaver, with full Elite gear. I used the following:
Demon Spawn Woods
Savage Beast Iron
This way my character had the maximum amount of Power and a very high stat for Strike, Spin and Putting. But most importantly, Frank's ability, Rocket Launch, will come in handy. I didn't use any boosters for my run. I used Astrid as the caddy with the following perks:
-20% Shot Bar Speed
+20% Rough Lie Boost
+75% Lucky Drop Chance
These characters are completely optional of course, especially the caddy. With this guide I will assume however that you'll use Frank because his Rocket Launch skill willl save you some strokes.
In my opinion it's the Par 5's that are really the most important ones to do right. For almost all of them a birdie or even eagle should be within your grasp. Par 3 on the other hand, are the most likely holes to cost you some strokes. Okay, below I've described the way I was able to get this achievement. I'm sure there's a more optimal route for some of these, especially if you're using a different character, but maybe this will help some of you. I advise, however, to from time to time use your own insight on how to apporach some holes. If you're already 6 below par at hole 9, be sensible and just try to avoid the bogeys instead of going for birdie on each hole. It would also be a good thing to hit -6 before you reach hole 15. In my opinion, the last 4 holes are among the trickiest of this course, so try to have a proper score by then. Anyway, here goes:
Hole 1: Most of the time I just settled for par here. It's really difficult to land it close to the pin on your first stroke, what's more, I found it more likely to get a birdie here from a chip/pitch shot from the bunker than a putt from the green. Just make sure you don't bogey on this one and continue.
Hole 2: I found this one to be one of the most difficult drives of the course. The default stick is the Wood 3, although my first instinct was to use the Wood 1, stick with the 3. Settle with a shorter drive, but avoid the risk of hitting the water hazard. Plenty of times I thought I had hit the perfect drive to end up in the water instead because of the steep slope to the right. For your second stroke DON'T PITCH. You might end up hitting the overhanging arch and ruin your shot. Use a normal shot and you have a decent opportunity to hit a birdie here.
Hole 3: The first par 5 and a very good opportunity for a birdie. I used Frank's Rocket Launch from the drive here to clear the water hazard, potentially saving a stroke. Second stroke shouldn't be too hard, draw it around the canyon on the fairway and for the third stroke pitch it near the pin. The green is fairly easy on this hole so it would be a missed opportunity if you don't hit a birdie here.
Hole 4: With a Rocket Launch, some fade and some top spin you can get the ball on the green with your first stroke if you aim directly towards it. The following putt is very hard, so just try to get it as close to the pin as possible and get that birdie.
Hole 5: Look straight to the hole, as there is a giant gap in the canyon that can take your ball straight to the green. Should be an easy eagle or double eagle even.
Hole 6: Fairly straightforward hole. The green can be a bit tricky, depending from which side you approach, but you shouldn't have much trouble hitting a par or birdie here.
Hole 7: I aimed my first stroke to the right of the big 'pillar' in the center of the fairway. From there you get a decent pitching opportunity to land it close to the pin. With a good pitch shot the green won't give you much trouble.
Hole 8: Draw it around the canyon onto the green, leaving you a difficult putt. Don't even try to go for the birdie here, the putt is downhill, so you'll easily overshoot it. Settle for par.
Hole 9: With a Wood 5 or Wood 3 draw it into the gap on your left hand side. You might hit the bunker, but if you do, you still have a good pitching opportunity. This is a tricky green, I found a par acceptable on this hole.
Hole 10: This is probably the most difficult drive on the course. I used the Rocket Launch here to make sure I wouldn't hit the water hazard. It's possible to do it without, but I found it too risky. With full fade you can hit it on the fairway past the water hazard and to the right of the two 'pillars'. From there you have an easy shot onto the green. This is the hole that can really make or break your score, I've hit an eagle at this hole, but also a +5. If your round is going well so far, don't take too many chances on this hole. If you've got some strokes to make up for (you're around -2), this is one of the places to do it.
Hole 11: Another one of those par 3 buggers. With full draw and a Wood 5 (don't use full power) you can get it fairly close to the pin, but the green is tricky. As with pretty much every par 3, settle for par.
Hole 12: This one isn't too hard. Just drive onto the far end of the fairway and pitch it back onto the green. Good birdie opportunity.
Hole 13: Easiest hole of the course, anything less than an eagle would be a disappointment here. You can hit a 400 yard shot from the tee if you hit onto the giant slope right between you and the hole. Don't worry if you hit a bunker or rough on the landing, it's still way better than going around. Besides, you're really close to the hole, So pitch or chip it near the pin. To make things even better, the green is relatively easy, so you shouldn't need more than one putt.
Hole 14: I opted for a shorter, Wood 5 drive here to avoid being underneath the giant rock in the center of the hole. Then with an Iron 3 PITCH onto the green. If you use a Normal shot here, you'll hit that said rock. That still leaves you with a long putt, so par is the goal here.
Hole 15: This is an annoying hole. Obviously you should avoid the bunkers at all costs, but that's not an easy thing to do. This is one of the holes I don't really have any good tips for.
Hole 16: Even with a Rocket Launch I wasn't able to reach the green in one shot here, so don't bother with that. Try to hit the fairway before and below the green. Don't forget to adjust your second stroke to the great altitude difference and you should be good here.
Hole 17: If you're in dire need of a birdie, with an around 270 yard drive you should be able to put it on the fairway with your first stroke. An alternative is to use your last Rocket Launch and try to hit the fairway on your right side. I found this very risky though. If you think a par is sufficient, use the normal route and a par should come without too much trouble.
Hole 18: Don't you love it when they put the most annoying hole right at the end. As with most par 3's, this one is a pain. I've never really been able to figure this one out, mostly because of the really crappy camera during your shot. This is often a Hail Mary for me, as it seems to come down to just luck.
As I said, I'm sure there are better ways to do some of these holes. If you've got some tips for specific holes, please share.