I would 3rd the caution due the prescription creams. I use them too and am wary of trying anything I make on my face because of it. If you still want to try something, you might want to consult your doctor about the recipe and see what they think just to be extra careful, though knowing most doctors, they'll just tell you not to try it. They should know if the ingredients are ok for your face or not though so it might be worth a shot.
If you go ahead, I think you definitely want to make it as gentle as possible (because of the acne creams and because it IS your face
) so maybe something like jojoba beads for scrubbing. As for oils, stick with light and non-acnegenic/comedeogenic ones. If you check Susan's (swiftcraftymonkey.blogspot.com) oil property sheets, they should tell you if an oil is light, medium or heavy and if it's acnegenic and/or has a high comedeogenic rating. I remember she mentioned one oil, though I can't remember which one (it may have been Olive, but I'd double check), can actually make blemishes worse, not just make you more prone to clogged pores and breakouts. Avoid those like the plague!
Other than that, since you ARE washing this off, I wouldn't think the oil would stick behind too much as long as you use light-weight oils.
If you're still concered about the oiliness, since most scrubs aren't meant to cleanse as well, I usually follow a scrub with my cleanser to remove any excess oil. If you can figure out a way to do it and have a cleanser recipe/base you like, you could also try to combine the two so it's a cleansing scrub and wash-in-one and that might help with oiliness.
Another option would be to make a mask with gentle and exfoliating clays that you could use instead of a traditional scrub. That would probably be easiest and least likely to irritate the skin, but I'm no expert. Looking at the Clay descriptions on Brambleberry.com,
Green Zeolite Clay "is fantastic as a mild scrub, natural colorant or as a cleansing agent, due to its exceptional absorption properties."
Kaolin is supposedly good for sensitive skin.
Rhassoul Clay "has the ability to absorb oil and impurities from both the skin and the hair."
Sea Clay "is ideal for facial masks" and "acts as a mild exfoliant and is thought to have many properties around detox and cellulite reduction."
Yellow Silt Clay "is fantastic as a mask base or in a cleansing paste."
I haven't tried any of these so I can't give you any advice, but it's another option that might be less harsh for your skin. And I should also add that I am not a medical professional so please do not take any of this as medical advice! :shock:
Hope some of this helps!