Ive been using different metal polishes for my HD'S for close to 30 years & so far nothing compares to "Wizards" metal polish.This polish comes in an old style band aid looking can, the polish itself is impregnated in a roll of cotton in the can,a chunk half the size of my thumb is enough to polish all the aluminum on an entire motorcycle.
After you rub on the wizards you buff it out with a clean rag then buff it again with a shammy,each time you buff the clean rags will end up jet black & you'll pull out every last stain in the metal.I have an old Shovelhead HD that has all cast aluminum instead of chrome & after polishing it with wizards the aluminum shines as deep & bright as chrome,the entire process is very fast taking me about 2 hours to do a complete motorcycle.
Ive used wizards polish many times on the chrome & stainless steel chasis of vintage mcintosh equipment that have silk screened lettering & the polish leaves the silk screen intact.
Most motorcycle shop's will carry this product,they may also call it by the original name which was (QUATOR) pronounced as water but its now called Wizards.
http://wizardsproducts.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=WP&Product_Code=W1101101213&Category_Code=