Amonia is an old trick that works well. You don't need to soak the grates in amonia, the stinky amonia gas is what softens baked on grease. Put a pan of amonia in your smoker and pull a trash bag over it and you will probably get similar results.
Try not to breath too much of the amonia gas that stuff is bad for you.
Don't mix any bleach with the amonia. It makes a poison gas that will kill you.