The last post gives you the idea of what works. Don't be surprised if you don't do it as good as he can. If you get desperate, have him show you what he does.
The VERY MOST IMPORTANT idea is that you need lube on your fingers.
If you wait until pre-cum lubes your fingers, you may have him all tensed up because it is so SENSITIVE and should never be done dry! (It should feel good from the start and just get better.)
Have a towel ready to clean up...you're going to need it...for your hands too.
One favorite is that you form your thumb and forefinger into an "O".
Take a tube of lube and lube the INSIDE of the "O". Then grasp just under the head and move up and down slowly about an inch.
(You may have to hold back the foreskin (if any) with the other hand.) Now take your fingers in that same position and go back and forth both ways while up and down slightly, like you were twisting off a bottle cap. You can rise up over the head rim occasionally, but go back to that same spot. This gives unbelievable pleasure because you hit so many sensitive areas at random and it is very powerful. You will feel his head swell up and the base getting hard. When he starts to cum, keep twisting...don't stop.
He will never forget that one! !
Let us know if this works for you.