^^^^ I'd just use some 600 grit on the plastic , not too smooth , then plastic primer , couple of coats , 1200 grit on the primer . 3 coats of top coat or until your happy with the finish , if you get a good finish you shouldn't really need to sand the top coat . Then 3 coats of lacquer thinly applied as lacquer tends to run if you put too much on , sand inbetween coats of lacquer if the finish isn't that smooth with 2000 grit
Make sure the surface is very clean , no dust etc inbetween coats , use a tac cloth .