Actually there's a reason y he feel abit uncomfy when his
foreskin is being pulled back... it is due to no lubrication..
therefore when u gif him a hand job, the feeling is not smooth.. he
might feel u r hurting him.. maybe u can buy some ky-jelly or use
natural lubricant (saliva) to help 'smooth' the sensation.
Actually on statistics, guys prefer blowjob more to handjob. Dun
think tat u cant gif him a gd blowjob.. jus treat it like u r
suckin a lollipop or licking an ice-cream? 
