From my experience, you need to go slow and keep things symetrical. This is the hardest part in doing it right and keeping it looking proper and professional. Files, diamond versions, make good work of it. They are in rough to very fine and can be done nice and flat as they are like a little paddle. Clean up with finer and finer as you go. Just keep vigilant about the running lines. You are rounding them over but still need to keep the line or it will look like it off angled and show up terribly with new finish.
Some like a file or even a rotary tool. Once again, it's not the tool used, it's the tool using it. Use it slow and steady and good results can be had with most proceses.
Some like sandpaper or cloth papers but you will need to mount on a flat surface to get edges and corners done straight.
You will go through the tennifer and lose that protection in the areas you need it most.
It will also need to be sand or bead blasted to get a surface texture back on it. Easy enough. Whoever will do the refinish should do that anyway.
Not much too it really. Get some pictures of one done and try and look at every line, curve or corner that was done to give you a guide and keep you getting all the spots.
I personally love the look of Sigs SAS treatment. It looks the smoothest out of any I've seen.
I would love to figure out how a large vibratory cleaner could be used to just hit the spots I want but they wouldn't be too specific. Would do every spot and certainly areas you wouldn't want to touch. Just wishful thinking.