sprayed inside cab and underside/firewall on my 90 replacment cab

used the rustoleum spray in bedliner with the bedliner spray gun.

good stuff and nice finish. yes you would need to tape it off stuff you dont want coverd.

I did the bed of my 88-440 truck with the hurculiner roll on = grity crap that has faded already in 2.5 yrs, grit will brush off by hand and leave a black chalk like crap on your hands. it will get redone with the rustoleum next.