yea... when i played a lot, i used to get chronic blisters on my hand and feet. adding layers / tape didn't seem to help. it almost felt better just to rip the skin off, douse it with rubbing alcohol, scream in to my arm for a minute, and then go back to playing.
but given today's hi-tech world, i'd be amazed if there isn't some good solution now. i wonder if the rules allow local anesthesia...?
i really doubt rafa does anything to numb the feeling in his hand. he needs the feel to make precision shots every moment. his dominant game is predicated on the fact that he makes very little unforced errors.