Do I need an etch coat before primer? My local paint supplier is trying to sell me a 2 part etch as well as enough paint to cover a truck. Do I need it or is he just trying to sell me stuff?

Ask him if he has a highbuild etch, they are 2 part (thats PART not PACK) and will mean you wont have to use any celly primer which is a bit too aggressive for GRP