Not an endorsement and just to illustrate, but you need to buy a selection of aluminum (non-ferrous) and steel (ferrous) carbide burrs like you'll find on this site + a variety of stones and sanding cones. The amount, shapes and lengths needed are specific to your application. You won't need one of each shape, but at least a couple for each type of metal. Use parrafin wax to keep the bits from clogging. Use a die grinder, preferably variable speed. Real porters don't port at top speed, but rather, with a flicking on-off to "throttle" the grinder at very slow speeds to control the cutting action. Remember, you can take you r time, measure and take more off, but you can't put it back on.
And now some Zen-like advice:
Like a Sunday drive in the country - Take your time, enjoy the view, become one with nature and the flow, don't miss stopping to observe something that you'll regret later. It'll be over before you know it and then you'll just want more.