My boyfriend and I both enjoy sexual intercourse and foreplay while I'm "asleep" any tips on pretending?

We have sex during our waking life as well as its great! But once in a while we like to spice things up with sleep sex. My boyfriend suggested this to me early on in our relationship and I said it was fine, he could do it any time. Sometimes I'm really sleeping (I occasionally take Rx sleeping pills for insomnia), others I pretend. Getting the play-by play from him the next day is so hot, it turns us both on immensely. I'd like to hear from those of you out there who enjoy this as well. Any tips on how I can play sleeping beauty more effectively for the times that I am just pretending?