Much of what you want to do depends on line pressure and the blasting medium. I've used that type of gun and sand and it will remove rust from car bodies in no time. Sounds like ground walnut shells might be what you need. I would call around to suppliers and ask telling them you want to clean up a piece of anodized aluminum, sometimes too much info is not good.
And use a test piece before you start blasting on someones gun frame. TF