Turtle wax on the cheap from wilko diluted in a sh1t shifter bottle about 10:1 with water. Rinse and then scrub with nice hot soapy water.
Never found proper cleaners much cop, if it’s fresh and still wet it rinses off anyway, if it’s baked on, never found the cleaners to work all that well (and you use a whole bottle trying).
In fact if it’s baked on, it’s usually a partial disassembly job anyway – chain, cassette and rings go in pot of degreaser…