Just tell them how you are feeling for example, "I love the way your dick is pounding my ass/pussy" and you can tone it down too, "feels good the way your dick slides in and out' just depends on your comfort level I think.
I totally understand that! My bf is in the military and we are apart quiet a bit. I put on a little masturbation show when we are together so he has something to remember when we have phone sex and masturebate over the phone. I love Kamasutra love oil ambrosia....