I've used this over oils without any problems,but I find it is not the best clear matt to use,as it is not always completely matt.
I mainly used it to matt aircraft after applying decals and it left a nice finish to the aircraft.
Ralph.
This is the best clear flat I've used. Airbrush several light coats for a completely flat finish. I'ts lacquer based so I don't know how well it would brush over other paints. I would recommend you experiment first. Good luck! Regards, Chuck