For those who want to use a glitch for this, the dashboard glitch has been patched.
HOWEVER there is a new glitch that will make things alot easier, and is similar to the glitch.
EDIT: This glitch still works as of March 10th, 2014. Thanks MiserlyPluto459 for telling me about that.
I would suggest at least trying this legit, although you should plan at least 3 hours+ for each mission to do it legit. My average time for doing it legit was 2-4 hours with my record times still being 1-3 hours so it will take some time, but it is rewarding to know you got one of the most difficult achievements legit. I would post my tips and a guide for doing it legit, but there are already several guides for that.
To do the glitch you must:
1) Start whichever level you need for the achievement at the start on EASY.
EDIT: You MUST be in the game lobby for this to work. I had someone join during the second chapter of No Mercy, and he did not get the achievements.
2) Rush as fast as you can until you get to the final saferoom (the start of the finale). Do NOT take the bar off the saferoom, or even open the door.
EDIT: Some people have told me that opening the saferoom door does not effect the glitch, but every time I have used it I have left the bar on the door.
3) Vote to Return to Lobby
4) Start the FINALE of the same level you ran through on EXPERT.
5) Beat the Finale, get on the rescue vehicle.
EDIT: In order to get the achievement you MUST make it onto the rescue vehicle, if someone gets in and you miss it you will have to start the entire process over again, meaning you cannot simply reselect the finale, you will have to run through the whole time.
This glitch works for anything that the dashboard glitch worked on, and any achievement that requires you to play the entire campaign.
Achievements that you can win using this glitch (but you do need to go through the finale and earn these):
Do not Disturb
What are You Trying to Prove
EDIT: Sorry for those who would like help from me but I can't run through these achievements anymore. But if you need any further explanation send me a message.