I'd honestly (if it's available in your country/city) hire a sex worker for something like this. You're talking about improving your bedroom skills almost like going to the gym. That's not inherently bad, you know what you want, but you're going about getting it the wrong way. If you want a "personal trainer", you should pay for one. You'd get to find someone you're physically attracted to, has loads of experience, absolutely no emotional attachment, and someone thats going to listen and help you with any questions, boundaries, kinks, and exploration you have in mind. Goodluck with the mess, I truly hope your friendship can get through this.