How can I make it shinny again? Can Melamine foam work?
I do not want the polisher to be acidic enough to melt the plastic
Any metal or car polish will work fine. I use Nevr-dull. Also 0000 grade steel wool works good.
will it melt the plastic
No it doesn’t affect the plastic. I don’t know of any metal polish that does.
IF i use it on a metal yoyo with splash/paint on it will it rub off the paint.
Only of you rub too hard. Car polish is made to re-shine paint, which involves some removal. But why would you want to use it on a metal yoyo with splash paint? If it needs cleaning just use soapy water, rinse & dry.