IDarK VorteXX's solution is spot on. This achievement can be a little bit tricky as it's tough to keep yourself in good shape whilst making sure all 6 friendlies are not being smashed to bits too!
I've put together a video which will hopefully give those struggling a bit of help with this section of the mission. This video is recorded on Heroic difficulty - Solo starting from the beginning of the mission.
Please note: You CAN start from Rally Point Bravo and still unlock this achievement if you've played and completed the mission once already. (Thanks to
https://www.trueachievements.com/gameman9.htm for the confirmation on this)