Brasso

I do not think I can answer your question directly, but I do think a lot of it has to do with the applicator you are using, how much pressure you are applying, and the rotational speed of the axle itself. I certainly can vary how aggressive I am polishing by altering those few things and do intentionally at the different stages of my axle polishing.
 
Brasso is more of a "chemical cut" than actually with grit.

If you use it for its intended purpose, you don't even have to rub hard at all or polish fast....just slow swirls and it "melts" the patina off brass. Don't know what reaction it has with Derby axles. I've used it before but just now really thought of this.
Maybe it does have a little grit, but I don't think that is its main way of polishing.