Ron can correct me if I'm wrong...
You can put clear bra over OCP, but not Gloss-Coat or OCP+ as the latter two are a slick finish. You can also put OCP on top of Xpel clear bra film, which they actually recommend.
In a dream world, you would put OCP on the paint, lay down Xpel, and then coat Expel with OCP/OCP+. That way, if the film ever has to be removed, OCP is still protecting the paint, like the rest of the car. Make sense?
From what I've been told, OCP needs to cure for 7 days before film can be installed over it though.