Most people use the support hand to remove and replace the magazine. If you're reloading from empty, you'll then need to use your strong hand to work the bolt. (If you're reloading in a lull, you'll want to work the bolt anyway, just to be sure).
Recently I've been practicing using the strong hand to remove, stow and replace the magazine, then work the bolt. Seems a little faster and smoother.
For the ultimate in quick 'n dirty, grab the new magazine with either hand. Hold it horizontally, edge forward and run it along the bottom of the trigger guard to press the magazine latch, then rotate the magazine to knock the old one out of the well. Put the new magazine in and work the bolt. It's surprising how quick this one can be accomplished. But only use it of you don't give a crap about the finish on your gun and mags. I don't remember where I read this technique, but I think it's one of Louis Awerbuck's.
See what works best for you.