This isn't too bad of an achievement, especially if you're doing it solo. You can command your AI team-mates to get into vehicles without hurting the achievement for yourself, which I recommend you do at every opportunity. They really act as bullet sponges and as long as you let them lead somewhat, most fire will be directed on them.
The hardest parts will be when you're meant to get in the scorpion, as your team-mates won't use it. There are a number of laser turrets firing on you, so I recommend trying to save a power weapon for that point. There will also be parts where you a in an open area waiting for a door open. At this point, you want to head along the sides and up a platform where snipers and turrets are waiting. Use these to your advantage.
Video guide can be found here: