Take those less expensive, rounded plastic hangers and make non-slip hangers out of them!!!
Using your hot-glue gun, run a bead of glue down the top of each side of the hanger and allow to dry - DONE. That was easy! I did a wavy line down mine, it seemed to be a little easier than trying to make a perfectly straight line (which it doesn't have to be).
(This is not original with me, but I can't remember where I saw this tip/trick, so unfortunately, I can't give credit to my source ... I'm bummed, because I always like to credit my sources -it's the English major in me!)