I go to the dollar store and buy the knock off (cheap) oven cleaner. It will strip grease and paint off steel and cast iron parts. It will work on aluminum but you have to watch it because it will eat the aluminum if left on it too long. If you have an anodized aluminum part it will remove the protective coat and color if it has it down to the bare base.
When I have something I want to clean like new (car, truck, tractor, lawn mower, ect) I'll tear it all down and soak it in the oven cleaner. I then pressure wash it all and normally all that is left is the deepest rust. I then media blast it. If you reuse the media it helps keeping it from getting contaminated as fast.
It is just like aircraft stripper (some mean stuff) so wear all the protective gear. I have chemical burn scars on my arms from being young, dumb, and bullet proof from the junk.