If he doesn't pull off his underwear, you do it. You're entitled to full access to that cock if you are charged with blowing it to completion. So don't be shy - pull them off him then lick his balls. Show him you mean to do this right. You're entitled, do it.
Wish I was between his thighs and lick his balls and hole while he wanks and moans. I imagine how I kiss and lick his big nips and pits while I stroke his cock and how I caress his body while I suck him until I feel his cum on my face or chest.