I had a bunch of stuff galvanized for my truck.
Prior to galvanizing, I had to remove all of the paint. If you're diligent and into that sort of thing, you can strip it yourself. I tried for a while and ended up taking it some place to have the paint removed (acid stripped).
This might vary by galvanizing shop but the place I used (Seattle, WA) wanted me to wire up the pieces on a frame. They would then send the frame through their process. After getting the frames back, I cut my pieces out and cleaned off the excess zinc.