I have done this, it is easiest to do man behind, double end dildo from anal to anal. You will need special dildo that has skeleton inside and narrowed mid section. He needs tight trunks to support dildo, maybe tight cock ring to keep dick hard enough. Have fun, I have a prostate orgasm every time!
I love this slip on tool. It is no just panty to wear, but a tool to turn enhance woman to have cock. Strapons don't feel quite like, because woman don't have anything inside. I think this tool enables her to cum penetrating his lover's asshole.