its really not a bad idea to wear some 18 oz. sparring gloves hitting the heavy bag. outside of the fact that if you hit hard enough you are putting a tremendous beating on your hands, which the extra couple oz. of padding will help, it also doesnt hurt to get used to having so much excess weight on your hands.

as far as wrists go, start doing some wrist curls and reverse wrist curls to strengthen all the small muscles surrounding the wrist and leading up into the forearm and down into the knuckles...muscles that are VERY OFTEN neglected.