This solution is quicker then the other two. Make a private plant the bomb match, you don't need anyone else. It's best if you start as Warface(the team that starts out defending. Kill yourself, (The quickest way I've found to do this is actually place a claymore as an engineer at your feet and shoot it) five times, until you switch teams. (Engineer Recommended) Grab the bomb, plant it, and kill yourself.
This way you don't ever have to just sit around waiting for the timer to tick down.
Repeat as many times as needed.