What does one use to clean burnt grease inside and outside of pans?

Bars Keeper Friencd at walmart

A thick paste of baking soda and water. just let it dry the stuff will be loosened.

oven cleaner

I've used baking soda and white vinegar. Or you could also put the pans in a plastic garbage bag with a cup of ammonia. Seal the bag and let it sit overnight. Don't pour the ammonia into the pan, just let the cup (or small bowl) sit in the bag with thepan. The vapors loosen the grime and makes it easier to clean. Make sure you leave it outside because of the vapors. I did thisonce and it really worked. I am planning on doing it again with my oven racks. I have a self cleaning oven and I never leave the racks in while it's cleaning so they need to be clean by hand.

Aluminum coated pans or stainless steel pans?

I don’t think aluminum will tolerate ammonia and I would look into that, just in case.

S/S then I’d use a green nylon scrubbie and Comet/Ajax.

I've had good luck soaking overnight in Dawn Power (not the regular Dawn dishwashing liquid) and very hot water. :)