If the area you are working on does not turn black you have a coat of clear over the aluminum and go to a different type of cleaner.

For those of you that have never polished aluminum before... When you use a product like Meguiar's Hot Rims Mag & Aluminum or any other brand of aluminum polish you end up with a black film on what you are polishing the more you work it. This black film wipes right off. It is just part of the process.

In simple terms, the black residue is oxidized and deteriorated aluminum, there could be some chemical reaction taking place with the cleaners and the aluminum but we doubt that is the case as all metal polishes do this and in most cases there comes a point when you get aluminum so polished that to continue rubbing it with fresh metal polish doesn't generate as much black residue as when you first begin. 

By the way, we've polished a lot of aluminum by hand and the results have been stunning.

TIP – A Dremel tool with the correct size and type of attachment can help and speed up this often overlooked task. 

Polishing "aluminum" is similar to polishing paint. It requires using various grades of abrasive polishing compounds starting with a heavy cut metal polish and ending with a super-fine, finishing polish (depending on current condition). Some aluminum polishes (such as the ones below) are designed for application with either a dual-action or circular machine polisher .

Blackfire fine cut aluminum polish 
Here's an example of a 2 step polishing that would work: 





I would definitely buy a polish specific to the metal you'd like to polish that is designed to give you the result...  (like a Mirror finish)