This solution is the strategy i used. I can easily PaP all 3 weapons by wave 10 doing this. This method is best done solo. Also, ALWAYS BE AWARE OF WHERE THE ASTRO-TROLL is, this is vital. He can seriously ruin your day if you're not careful.
1.At the very start, try to make sure the perk available at hangar 18 is Juggernog. If it isn't, restart (you don't have to, it just makes life a lot easier). If it is Juggernog, you're ready to start.
2. Once the zombies start spawning, don't waste any ammo, run around knifing them as quickly as possible (on a good run you can get 1500 pts, on a bad run about 1000). Once you hear the alarm for the teleporter gate lifting, go to the corner behind the PaP machine and wait for the nuke alarm. Once the nuke alarm sounds, carefully begin running a big circle around the map, getting the zombies in a straight line.
3. Once you have no more spawning and they are all chasing you, cook a grenade and wait for the crosshairs to pulse 3 times. turn and throw it at your feet, this should net you about 500-600 points. do the same with your second grenade. After you run out of grenades, continue running circles, turning to pop shot the train of zombies when you feel it's safe. continue this until you run out of ammo. you should have enough for the Juggernog. Once you can afford it, run up and buy it and head straight for the teleporter.
4. On wave one one the moon, let the zombies in and begin knifing them as you did to start at hangar 18. If you're lucky you'll get a good power-up like double points. (if you have Juggernaut, be careful of the astronaut as if he grabs you he will take it away). Once the round ends, repair the windows.
5. on wave 2, do the same, let them in and stab them all to death. Once all the zombies are dead, board up all the windows again. (if you don't feel confident, or you just wanna be safe, you can buy quick revive now as well)
6. On wave 3, open the doors and buy the m 14 off the wall. you'll now be holding the catwalk area. try to stay towards the middle of the cat walk. shoot each zombie twice in the chest and then knife them once to maximize your points.Leave one alive at the end of the round (note:you can't make crawlers yet, so don't try to). Begin opening all the doors leading from tunnel 11. make your way to the conference (or pyramid room) and turn on the power. you should have enough points to make it to at least the laboratories at this point.
7. once in the labs, look for the hacker on the desks. there are 2 possible spawns on each level of the labs. if you're lucky, it will be on one of the first 2 floors and you'll be able to hack the door to the to the top floor of the labs. if you don't have access to the hacker yet, go back and kill the last zombie of round 3 and head back to the catwalk area outside the spawn area.
8. repeat the method you used for round three. this time put 3 shots into the zombie's chest and knife them to maxmize your points. If you feel like you're getting over run, you can also just go for headshots. Once you start getting to the end of the round, make a crawler using grenades.
9. If you haven't already, open the door to the top floor of the labs and pick up the hacker device. Hack the door to your left and go outside. this is where you'll really start racking up points.
10. If you can afford it, buy the AK74 U off the wall outside. This is a great weapon to have because if you begin running low on ammo you don't have to waste 950 to get a gun from the mystery box, you can just grab ammo for 600.
11. From round 5 on, this is what you are going to do. At the start of each round, run circles around the rock outside. continue doing this until you have a train of zombies following you and you see no more zombies spawning (only sprint if you have to avoid zombies coming at you from the front, this will help line them up for you). Once you get a good train going, turn around and unload on them with the AK74.continue doing this until you notice their numbers dwindling. Once there are 4-5 left, cook a grenade (3 pulses of the cross-hairs) and make some crawlers. kill all but one. if you are confident about running circles, jump to the teleporter and do the same thing at hangar 18. continue killing until you run out of AK74 U ammo. Go back to the moon and buy more ammo for your AK. Continue doing this until you can afford the Mule Kick perk, which is outside where you have been running circles. For your guns, you should currently have the m14 and the AK74 U.
12. once you have enough points from rinsing and repeating step 11, go buy the olympia from the catwalk area, by tunnel 6 (it is the cheapest weapon). head to hangar 18 and PaP either the olympia or the m14. At this point you can grab your weapon and leave immediately and go back at the end of each of the next 2 rounds and do the same for the other 2 weapons, or, IF YOU FEEL CONFIDENT ABOUT RUNNING CIRCLES, you can actually PaP all three weapons in one go (if you can afford it of course). In order to do all three weapons in one visit to Hangar 18, put the olympia in the Pap machine, begin running a circle. once you pass the machine, hold x and grab it . Run another lap and put the m14 in the machine, take another lap and grab that on your way by the machine the next time. finally do the same for the AK74u and the achievement will pop, once you pull it out of the machine.
sorry this is such a long solution, but i wanted to be very detailed. if you are confused about any part, pm me and i will answer any questions you may have. i can also take time to show you exactly what to do if you really want me to and i can find the time.
please, if you negative vote, put the reason in the comments, so i can better make this guide and future guides.
i have also attached a video from Achievement Hunter on how to run circles at hangar 18 if you need to see what to do (don't be confused as it's for the perks in spaaaace guide). once you get the hang of it, it's not too tough to do and you will get TONS of points doing it.
 the earliest i've gotten all 3 PaP'd doing this method was round 7