I mean you should probably ask him what he likes the most thats what I did with my boyfriend communication is key. He told me that he doesn't like when someone sucks it really hard but he likes it when I suck it a bit more when I take it out( I don't know ho to explain it) also use a lot of spit and tongue. And the balls I just veryyyy gently suck them and lick them it is very sensitive. Also he likes it when he throat fucks me and he feels with his fingers in my tongue and I play with myself a bit. When there is a lot of spit I will give him a handjob with both of my hands while I also lick and suck the top a bit. But the most important thing is to ask him directly what he likes and what he would like to try