Bull fucken shit. Having sex on shrooms was unfucken real. When my wife had her orgasm I thought she was going to die. She looked like she was in the middle of an exorcism and was screaming her head off. When it was my turn it felt like my soul was getting sucked out of me through my dick. (very cool experience)Of course if you take too many shrooms you are going to be incapacitated. So I would aim for a level 3 trip. As long as you have some capabilities such as being able to walk and convince your girl to get horny you'll be cool.
The easiest way is to suck on her finger. She will understand very quickly. (feels like your body is melting)
If you get her to come (very likely, she will be very sensitive) she will look at you as if you were GOD!!!!
Some of the responses here I don't quite understand maybe shrooms affect me different. Then again my sexdrive is like a runaway locomotive. hahaha!!!!