The regular "purple" degreaser works well. Simple Green is one of the
recommended cleaners for cleaning SCUBA regulators with an US cleaner.
Most any non flammable cleaner that won't attack the SS tank or the part
will work fine.

I've had luck removing stains with ammonia and dish soap. Also great to
clean my glasses and the SO's jewelry

"The Kid" put carb parts out of a '65 'stang that had been in a junk yard
for years in a little can of carb cleaner and held it in the tank, floating
and guided by a couple strings. parts looked like new.

Karl