I used to have an extremely active sex life, in my head. I've hooked up a fair number of times before I got married, but never had anything long term until I met my wife. It's never translated 100% into the real world, though. I'm able to function, but it can feel like work at times. Here are some things I've thought would help:
1. Talking about ones desires, and going over how it will happen, planning every single detail, then acting. I think most people are much more spontaneous, but I think for someone with ASD, planning is a very important part of how things work. At least this is the way I work with every other social event, so why not sex? It's really not that abnormal to talk about one's desires beforehand as well. Go ahead and work out every move if you wish. Don't worry about "success" or not, just get used to the idea.
2. For some, talking about it, and keeping touch to a minimum may be enough. It might be that one wants companionship, but not necessarily to be touched by that person. So, fine, don't touch each other, but you can still masturbate, talk, and share fantasies. You can still touch, but maybe not quite as intimately as others.
3. I have a feeling that most people on the autism spectrum have "abnormal" desires. It's just my guess that since people are so overwhelming, that we probably focus our desires elsewhere. Fine, don't be ashamed. As long as you're not hurting others or breaking the law do what works for you.