heres what i do for those nasty controller cases with who knows what on it.
First i remove all the electronics from the case and get all the plastic pieces then soak the pieces in 1 part bleach, 5 parts hot water. let it soak for 10 minutes and then i use an old toothbrush and scrub all the crap out of it... makes the customer think its a brand new case!!!
If there is stuff that won't come off after the first wash... dry the case and use a bit of isopropyl alcohol or "rubbing alcohol" and wipe the residue off then rinse & dry.