Is there a good way to clean the aluminum on the alternator. should it be painted or left plain. can it be taken apart easily?

 

I completely disassemble my alternators, glass bead both parts of the case, and then paint them with Krylon "Dull Aluminum" ,which is very close to the original cast aluminum colour. The paint is not necessary, but it will keep it looking fresh longer. Read the assembly manual to see how the brushes fit back in. There is a trick to hold them in place.