Some vinegar and hot water in the pot for some time will loosen up the guck. It might have to be repeated. If it has to be done again, just vinegar will clean it. This works real good.
put cola in it and heat it up
Soak it overnight with a degreaser and detergent, then use a "wire dish sponge" (Chore Girl) to scrub it. It will not scratch. A lot of elbow grease, but it will work.
Put hot water in it with some dish soap, and let it soak for hours until the beans start to come loose.