Spinners are one tool for the tool box, they work great with some materials, crap with others.
I've had good luck making spinners using a ball end mill in the chuck on the tailstock of my lathe and cutting the end of round bar. With spinning, they honestly don't even have to be hardened for softer pin materials, the tricky part is just polishing the inside of the spinner, as any imperfections will show on the pin, although if you're buffing them afterwards it's no problemo.
The nice thing about spinners is that you can get down into the texture of stag if your spinner is made properly, and if the pin is tight fitting, you can usually spin the head without any elaborate support on the back side that requires 4 arms to hold the work on top of. It's still a technique you have to be careful with, I often see really crap looking spun pins on stag handle folders, with burned out, splintered edges (because people are using the wrong pin material), and a big ring cut around half of the pin from the spinner cutting into the handle material. This is a pet peve of mine personally, and I think it looks like total ass.
Cup punches are another useful tool, as are cup burrs.
I use all of them depending on the situation, and the materials. With the cup burrs, you still need to peen the pin heads to swell and create a rivet head that holds the material together. You can then go back with the appropriate sized burr and cut them to near perfect symmetry.
Cup punches I'll use to get down into deep texture of stag when I need to swell more than I can reasonably spin, with materials like 410 and titanium, which don't spin very easily, this is often the only option IMO. The tricky thing is holding the opposite side of the pin in a lower cup and keeping it there while you're smacking the top punch without it bouncing out and leaving tracks in the pin. Usually this is in a situation where it's not possible to get down into this area well with a buffer, although with care you can do some work on them with a cratex point.
First thing to learn Manny is how to dome and polish them by hand, i.e. peening them domed and buffing them clean. I highly recommend making a pin heading jig/vise, do one side first in the vise, then peen the other side on the knife. It also helps to have a flat "anvil" for the opposite side with a small domed depression that you can seat the head on the other side in.
This is one of those techniques that sounds real complicated until you learn how to do it, and it can certainly be made to be complicated, but after you've peened a few dozen you'll realize it's super easy, except when working with advanced materials. I'd bet money I can set and clean a pin faster than most could install a corby and grind it flush though.
