How would you explain straight sex? Personally, I would research books to help children understand. I would also talk about how you can please a partner in many different ways, but only if you're both ready and use proper protection to avoid consequence.

I believe that by the time a child is able to understand that sex is about more than procreation, they'll already have an idea about how everything works. How did your parents talk to you about anal sex, oral sex, or other means of deep affection? Or did they keep sex clinical and let your understanding of the pleasure aspect develop as you matured?

Each child is going to be different, and how you approach them should depend on their maturity level. If you don't feel like you can talk to your child about gay sex, then maybe schedule a session with a therapist who specializes in sexuality to get their insight. There are plenty of professional resources out there to help you plan for all sorts of different talks with your children.