Once I razor blade the inside of the bowl, I use an SOS pad and Dawn soap to remove the rest. Both the SOS pad and Dawn soap are biodegradable so I clean the kettles over my lawn, sitting on a wrought iron table. I hose the bowl down when I'm done scrubbing. Multitasking - Cleaning kettles and watering the lawn.
Once dried, I hit the outside of the bowl with #0000 steel wool to really get a high shine.