This achievement is very easy to get in conjunction with the Wraith Killer achievement. Make sure to attempt this on the Uplift Reserve Flashback as Dutch. NOTE: Do NOT shoot or grenade ANYTHING. This will reset your achievement progress for Classic and that's not a fun thing. At the start of the level you can either assist the overturned Warthog or continue to the right along the outer wall. I recommend the latter as on legendary the grunts are fond of grenades and are able to stick you while you right the Warthog almost every time. As you make your way along the right side of the level, commandeer a healthy Warthog and boot out the driver. NOTE: Do NOT honk the horn. Aparantly Bungie regards the horn on the Warthog a deadly weapon. Honking it will count as a shot fired, so avoid at all costs. After removing the driver, make sure to swap your Spartan laser for whatever weapon the former driver has. Upon entering the passenger seat, the former driver will now be an unstoppable, infinite-ammoing, Spartan-lasering machine. All you need to do at this point is stay well back from the fight and let him/her work their magic. All Wraith kills made by your gunnery team aboard your Warthog will count toward your progress. The next few sections can get a bit tricky but the thing to remember is to stay well back and let your passengers do the work. If you lose a passenger, either restart at the last checkpoint or pick up a new soldier. Remember to pick up the laser if your passenger dies. Also along the way you will run into opportunities to swap Warthogs. If your team won't switch 'hogs, just take your Laser and give it to your new best front-seat buddy. If you run into Banshees, just move around. Make yourself a hard target to hit. The very last section takes some patience to pull off as you need to take out as many baddies at range as you can and move in on the last tank when the coast is mostly clear. You will know you are at the final section when you hit some switchbacks on the side of a hill that lead up to a covenant encampment. The encampment will have grunts hiding behind barriers waiting to stick blue fuzzy spiders to your head so be ready for that. After you take out the last tank you should get a pop-up for your Wraith Killer and after the small video interlude you should get Classic. Cheers and I hope it helps. The above is EXACTLY how I got both these achievements. If it doesn't work then try again. You may have accidentally hit the horn.