For baked on crud (oil and twostoke spooge) I have use easy off oven cleaner. The only problem with this is that you have to keep on top of it, it will eat aluminum if left on too long. It also eats up anodizing in a heartbeat (good annodizing stripper). for general cleaning I mix up a 50/50 mix of dawn dish detergent and simple green. cut a throw away brush bristles to 2/3 the original legnth (make it stiffer) and blott away. it should take care of 90% of the grime issues. But just like hair products say " wash then rinse and reapeat if neceassary".
Good ol engine bright from pecker "pep" boys will also do the trick, but it leaves a dust attracting residue:(