Being mobile and staying in the pocket are kinda conflicting terms. You cant really stay in the pocket if your gonna be moving around a lot. The key to having enough time in the pocket is making sure you have enough blockers to block his pass rushers and staying behind them. To use mobility to your advantage keep an eye on his pass rushers right as you hike to see which side they're coming from and move accordingly.
Madden's virtual trainer isnt good for much but they do have a pretty good part where you can practice being the quarterback and all you have to do is stay in the pocket and move around behind your blockers to have enough time to find an open receiver. It would probably help you with exactly what you wanted.
Subject: mobile in the pocket 
