Mk7 tailpipe, back box and plastic painting ?

[Jackmcgarry95]

So tomoro I'm painting the rear diffuser an the front grille gloss black, firstly do I need to remover the diffuser or just mask round it ?
Secondly should I use primer before hand or just spray 2-3 coats of the black as their already that matte colour ??

Also does anyone know where I can order a back box or a Tail pipe extension for the exhaust so it comes under the diffuser like the montune/milteck?

I can't afford a full exhaust