I totally agree w/lindac~it isn't necessary to strip the piece down to the original finish~that's just a waste of time for what you're wanting to do. Your biggest concern will be in finding a color of paint~I would start with a light beige or tan. For the edging, a combination of brown/black. I use a stenciling 'pouncer' for doing edging~load the paint, wipe off the majority, and with the flat end and a steady hand, glide it across the edge. If you want it darker, give a second coat, but don't load the 'pouncer' too heavily. Wipe off 'bleeps' right away. As for the glaze, you can use the same combination of black/brown, but water it down a bit, or use a ready-made glaze. Don't overthink....it's a lot easier than it seems. ;o)

I have had some good luck with a custom barn door manufacture in CA here is there facebook page https://www.facebook.com/DavesBarnDoors/?ref=br_rs tell him Mario sent you from www.MSDG.design

I would consider giving it a couple coats of a water based, flat finish urethane varnish. This will seal the surface and make it cleanable in the future, without making it look plastic.

I would use the same finish on all of the plumbing. Plenty OK to use a different metal finish for light fixtures.