Tips on Handjobs..?

So, I'm currently in a relationship and my bf and I have decided to take things slow (well, no sex at the moment).

Anyways, I've noticed that he takes a long time to cum...about 15 - 25 minutes sometimes. When I give him handjobs, he usually has to finish himself because my hand hurts. He doesn't complain about it but I'd like to be able to finish for him.

Can anyone drop some tips to make the handie a lot more satisfying and make him finish faster? I don't have any tricks down, just the regular 'jacking' motion. LMAO.