It’s not easy but this would be the first step! I had this same problem with my boyfriend, and we would talk about it, and after several months of getting more comfortable and practicing with him more, he was able to it with his hands. Eventually, after another month, he could do it through head. With sex, i will sometimes touch myself while we do it so I can cum, otherwise he’ll have to stimulate me a lot beforehand. It’s a slow process but it works and we are constantly improving!