When my 'Dh' admitted his affair, he gave me full disclosure.
Regarding the 'actual sex' , I decided that I didn't want the full details of how, duration, positions etc.
But I also told him that I assumed it was the best sex he'd ever had, real down and dirty mind blowing orgasmic,with no inhibition and that was what I have worked on in my head - the worst senario.
As we had the conversation , I also told him I neither wanted him to confirm or deny my assumption.
I have no confirmed scenarios in my head , so I don't have confirmed 'pictures' in my head to contend with.
It works for me - wouldn't expect it to work for anyone else. No one can say what will work for you - but you.
I know they had sex , that was enough - for me, how would the details and descriptions help me.
To be honest , for me the 'affair' - his emotional and time contribution , the betrayal of actually choosing to have an affair was 'worse' than the sexual acts they performed within the affair. Again, I appreciate that could be my personal experience and not everyone reacts the same....
Good luck with what you are facing.