I usually just use a damp cloth. If needed, I'll go over it with a mild soapy water, but that requires multiple passes.
I haven't cleaned it in about a year (since I still haven't finished the dang project), and it isn't really that bad.
'09 PSM G8 GT - OPG Intake, DOD-Delete w/ Stage 1C 218/229 .600 Lift 117.5LSA, Kooks 1 7/8 Mids, Solo Axle-Back w/ X-Pipe, SuperPro Bushings (Front and Rear). BMR Sway Bars (Red)
"If you want to criticize someone else's work, be sure that your own is in order first."