Custom Car Carpet Custom Interior Question?

Custom interior question? - custom car carpet

"Committee" behind the back seat of my car is carpeted, and it looks like fiberglass ..... My question is, could this connection be used to give a smooth appearance that colors ....
Ie, a number of filler, then sand, prime and paint to use?
and is able to absorb heat when the sun shone through the window ....
Ideas
(Custom panels are not) for my car