For long term, you metal will kinda get dull.And Brasso will kinda like "eat way" the metal part.
This is how I will use Brasso:-
1) Follow the instruction on the Brasso, I.E use a cloth and wipe around the metal parts and rub hard enough. After that, use a new clean cloth to wipe off any Brasso on the metal parts. The metal parts should look shiny now.
2) I will Use another clean cloth, dip with Zippo, and clean the metal parts again. And look at the cloth, it s DARK! means that even thou the metal look shiny, but the Brasso Chemical is still there. So i continue to clean the metal parts with Zippo until its really clean (from the look of the cloth that you wipe)
I seldom polish my bare metal yoyo now adays as it really takes up your time just cleaning one yoyo. So i will clen it once in a while like once per year? haha...
Well, as long as the yoyo can be played and I dont really think that a cosmetic look is that important.
Well, it's just my point of view.