Here's what I do: 1.. For stuff in fairly good shape I use Simple Green and a Black and Decker "Scum Buster" rotary brush that uses the B&D rechargeabe batteries. I use the soft brush attachment. I usually remove the case and take it out in the driveway with a hose. If it is really yellowed I use Purple Power this will remove some , but not all of the yellowing, but it can stain metal so be careful. Simple Green is safe and works great for dirt and grime. 2.. For magic marker and stickers I use Goo be Gone and elbow grease. 3.. To finish things off I use automobile protectant Looks alot better after that.