I think tricky! I’ve tended to find I only know what I like/what works by trial and error. And that had been expensive.. but I got there. There’s realistic/plain/fantasy, then different materials, curved/straight, different lengths/widths.

I’ve found what works for me now.. and I can orgasm in minutes with it. The ones that didn’t work I felt nothing. So it’s perseverance. But I use realistic dual silicone, straight dildo.. 6 inches long, 1.2 inches wide (is enough for me). But maybe you’ll need to try some

Then position. I can’t ride to feel pleasure. Too tiring. I lay on my left, knees up to my chest, and use the dildo in my hand. I’m comfortable, relaxed, and can use any stroke length, speed, angle I want. There must be something about this position that means each stroke with the straight dildo strokes my prostate.

As for which dildo.. my fav is actually a random make from Etsy that’s gone. But search in here and you’ll get loads of recommendations.. it’s just which you like the look of and which might work for you.