(IMO, anyway). I bought a spray gun from Al's Liner, along with their HNR (heat & noise reducing paint), and their spray-on bedliner.
Spray gun. This is more like an texture gun; it has a 6mm(!) nozzle
The Heat & Noise Reducer is some kind of ceramic paint; its supposed to be pretty good at what it does so I figured why not.
The test patch, dialing in the gun mostly
...and the whole underside sprayed! Went up into the wheel wells, and up the firewall
It goes down pretty easily
Theres a slight texture to it; I suspect with some more adjusting I could get it smoother though
The texture is a non-issue though, because of the next part: Al's Spray-on Bedliner
This is a 3-part polyurethane bedliner, that is fully tintable. On the left of the pic is a small bottle of surface prep, plus a bottle of my color tint: black
I recommend some kind of respirator, this stuff is wicked! (im not joking)
...and holy crap its done!
This part goes FAST. They claim the kit, after mixing, has to sprayed within 20 minutes or it will start to cure in the gun. Well no worries there, moving along at a decent pace you can spray an entire kit in ~10 minutes The whole underside took 2 kits, glad I bought an extra one when I ordered em.
I sprayed the whole underside, up into the wheel wells and all under-body xmembers, and halfway up the firewall as well
..and the money shot: This stuff looks (and feels) exactly like rhino or Line-X
I am super impressed with it, I think its going to work awesome. Its ~$85 per kit on Amazon, so it cost me ~$170 to spray the underside. Im going to order 3 kits for when I spray the interior just to make sure I can get it as thick as I want it. So it works out to about half what the local Rhino/Line-X dealers charge.