Regardless of the brand you use (and several companies offer multi-levels of aggressiveness in metal polishes, Meguiar's and Mothers included), I'd suggest you use a cordless drill at a low (300 rpm or so) setting.
A drill is more uniform in speed, so you'll get a more uniform result. You'll also need to make sure your tool/pad used is compatible with the polish you're using - aggressive pad with an aggressive polish.
You'll need to go through multiple steps, reducing the level of aggressiveness with each step, in order to come up with a quality finish, just like with paint.
Tape off any areas you don't want to come in contact with the polish. and, most importantly, make sure the finish you're working on is bare, polished aluminum - not coated or having a hyper finish.
Good luck.