OK, so I haven't *done* any, but I've read a fair amount. I have every confidence that I could go out in my garage and get started, mess up a few while I learned what *not* to do, and be fine.
I'd favor the *least effort* approach to getting started. There's an article by Phil Duclos called "Give Metal Spinning a Whirl" which outlines a *very* low-impact approach to metal spinning. You only need to make one or obtain 1 spinning tool, cobble up a tool rest (which can be as simple as a piece of rectangular bar stock clamped in a lantern tool holder), chuck some wood (by standard means, although the metal spinners have faster, more secure ways for production), turn a form. You need to be able to anneal the metal if it's copper or brass; aluminum needs nonesuch. For annealing you need a torch, a kiln, or so, that can get you to 1200 degrees or so.
I have a couple of books about metal spinning, at least one is from Lindsay Publishing. Old books are fine on this, and it's not a subject that gets written about much in current literature.
There's also a nice article in Projects Ten from Village Press -- the guys who publish Home Shop Machinist magazine (get it for a bit of a price break from caboosehobbies.com). That article talks about *many* different shapes of tools, examines a production spinning lathe, and goes into detail about modifying a chinese metal lathe to be an efficient, custom metal spinning lathe. I personally wouldn't go that route until I had tried Duclos' approach first, to determine whether I could do enough without the need for *yet another* lathe in my garage (I currently have 2 woodlathes and a metal lathe, and am running out of room). I'd also want to see how much fun I had doing it, and how much demand I could see for the spun metal parts.
I like Duclos' advice -- don't *convert* anything. You already have what you need, or at least most of it. You might like more diametral capacity, but don't we all, for all of our turning work?
In actual practice, spinning looks an awful lot like wood turning -- large, smooth body movements, as much a dance as anything else, are the order of the day. There are some great Youtube videos on the subject.
Metal spinning can be dangerous -- the edge of that spinning piece is *sharp*. Please be careful.