Internals : Brasso metal polish, dremel machine, dremel's cotton buds polisher, clean clothes, electric motor sprays.
Never polish the vertical side ( piston lining ). That's carbon like lining is the natural seal for compression.
Electric motor sprays for cleaning the carburator's ( spray it from the fulel intake nipple and watch the sprays come out from the carb nozzle ), and for bearing cleaning
Always use plenty after run oil for storage and while re-building back together.
Externals : I have japanese brand ( G-SOX ) made for automotive engine cleaner, its like thick foam, and it works very well to clean the outside cooling fins. G- SOX also provide free brush as complimentary cleaning kit.