For me, buffing helps a couple of way. It provides a very high shine to the finish, it helps remove any tiny irregularities in the finish, and since I buff the length of the pen, and tiny marks that remain run lengthwise and are much less noticeable.
I did my buffer on the low-down. I got a MT2 chuck at HF for 15 bucks or so, 2 6 inch buffing wheels at Lowes, 2 adapters to mount them in a chuck, and 2 bushings to go from the 5/8th inch hole in the wheel to the 1/2 inch arbor in the adapter. Total expense, under 30 bucks, and I had already gotten the chuck to drill on the lathe, so that wasn't really an expense at all.
Takes me 15 seconds to set up the buffer, pop the mandrel out, pop in the chuck, mount up the wheel I need. I've got a multi-speed buffer that takes up no extra room in the shop, didn't cost much at all, and greatly improved the quality of my finishes.
Hope that helps,
Steve