contact paper sucks. get some free 3m sign vinyl or buy some oracal 651. that will give you a lot better results.
otherwise, after youve centered the mask on the disc, put your hand under the disc and, in small circles, press down on top of the transfer-taped mask from the center and radiate out towards the rim. the idea is to lock down the middle and then work your way out towards the periphery. that will eliminate most bubbles.
otherwise, after youve centered the mask on the disc, put your hand under the disc and, in small circles, press down on top of the transfer-taped mask from the center and radiate out towards the rim. the idea is to lock down the middle and then work your way out towards the periphery. that will eliminate most bubbles.