If you pull your factory deck, you have to replace it with a plastic filler that fits cd players..(Ihave done this, I do installing ) but once this is done is what I need help with.

theres is a small crack between the plastic peice and the dash, I want to fiberglass the plastic peice and the dash peice togeather and paint it matching (exterior colour).
can I just resun the crack or do I have to use cloth some how also.
I only ask cause I don't want it to crack a month down the line.
I also want the plastic peice and dash to have a smooth affect so I wanted to know if you can just sand and put a layer of resun also on all of it.

anyone done this or have knolage of some where I can see pictures it would help.

thanks.