Painting glass opaque black
Unless you have some particular reason related to plasti-dip's peel-ability to choose that, just hit it with some black paint, and be careful not to scrape it when moving it (indeed, hit it with some black paint, and then you might want to cover the paint with paper for damage protection before moving it, after you check that the paint job is perfect.)

I'd probably reach for a can of BBQ black by default, but pretty much any black paint will do. The windows in some of the old barns where I grew up had been painted black (with a brush) and from the outside looked like black mirrors, even though the inside paint job was not very smooth - the glass makes the surface from that side.

I would let the paint dry a good long time before handling it at all.