If you want to polish nickel, use a blue color polish ( whether its a compound or a liquid ). Blue is a coloring only polish. White is a buffing/polishing compound ( again liquid or solid ).
Mothers mag wheel paste ( white ) is good for cleaning and removing light scratches. Just use a cotton flannel and change spots on the flannel frequently. As soon as it turns black, move to a clean spot ( the flannel will turn black ). Finish with a blue polish if you want a really illustrious shine. If you only need to get the shine back, start with the blue.
Do this by hand, not with a buffing wheel. Unless you need to remove scratches. Just becareful using a wheel.
If you need more info, let me know, I polish and plate everyday.
Good luck
Todd