I’m still very early on my hormone regime, but over time estrogen has the effect on trans women’s penises of thinning the skin and kind of “atrophying” the penis. Eventually it becomes more like a big clit, so you can stimulate it the same way you would a cis woman’s! Orgasm isn’t always the end goal, pleasure can be nice in its own right, so rimming and oral, especially focused on the head, can both help a lot there. Also, prostate orgasms are a thing! Stimulating the g-spot through penetration can be intensely pleasurable.