If you ask for advice, I'm sure he'd be more than happy to offer it to you
"what do you usually do to yourself?" is one thing I would ask, since that opens the door to the discussion in general. He may talk about that briefly, or give indication that he doesn't like what he normally does, and maybe slip in some advice on what he wishes you could do differently. who knows...
You never know until you ask, so go for it
Nothing sexual should ever be a single-person endeavor. Cooperate and learn from each other ^^