One technique for speeding up learning the muscle pass without hurting your hands is to switch hands every ten minutes. Not only do you end up being able to perform it in both hands, but it gives each hand time to rest and recuperate, and you won't end up with the damaged hands that some people report when they're learning it.
However, I reckon the key thing is to firstly make sure you're learning the proper technique (I think two complementary sources are Reed McClintock's "Classic Palming with Coins" and Shoot Ogawa's "Master of the Muscle Pass"), then I would say a couple of hours a day for about two weeks should be enough to give a workable muscle pass. This is for "Coin That Falls Up" purposes. However, if you want to use it as a hidden sleight then I would suggest a lot more practice, and rehearsal within the context of a routine.