I agree with others here I think hand feeding helps build trust (plus it's a way cool interaction you can have with your cham that isn't to stressful for him/her), I don't think they would forget how to hunt, but if your worried about it (or just want to make sure he/she's getting some exercise) you can just hand feed a few a day, or every other day and free range the rest (best of both worlds)
Maybe make the hand feed ones a treat (such as a worm or favorite food)