The best way to get baked on grease off of aluminum pans is to take some easy off oven cleaner and spray the aluminum pans with the easy off oven cleaner.
Allow the oven cleaner spray to sit on the aluminum pan for 30 minutes or so to allow the easy off oven cleaner to break down the grease.
Just like the easy off oven cleaner works to clean baked on food and grease out of ovens the easy off oven cleaner works just as great at getting baked on grease and baked on food off of aluminum pans.
Then you can soak the aluminum pan in some hot water along with some soap.
Just make sure you wash the easy off oven cleaner off the aluminum pan so that it does not leave a taste to the food you bake in it.
I try to wash my aluminum baking pans often and soon after baking in them but if there's baked on grease or baked on food I use the easy off oven cleaner to clean the baked on grease or baked on food off the aluminum baking pans and it has always worked great.