Hi, I recently had rubber banding treatments done on internal hemorrhoids, done one per treatment. I had no pain! Every one is different but I had no trouble. However, I do not know about a skin tag, sorry.
The doctor uses what to me looks like a little gun (kind of) and just snaps the rubber band on. It should be painless, it was for me. He said you might feel some tightness for a couple of hours but I didn't. The procedure took maybe 1-2 minutes if that. Then it will fall off from between 1-7 days. I never saw anything but it worked.