Not a lot. Go to a scrap yard/second hand car parts dealer and get another set of rear car seats and floor fittings. It would take hours to try and remove all that paint, and when it dries off a little it will be almost impossible.
I'm with Eric too, If your insurance covers you maybe you could use them. Depends on your insurance excess compared to the cost of second hand seats.
All I can suggest in future it to put the paints inside another deep container.