Try POR 15 paint. I no its pricy paint but tough as nails & a little goes a long way. It would be a lot of work tho because you would have to scuff everything the paint tuches so it will stick good. You also need to buy the Marine wash & Metel Ready to do it right. I painted all my skid plates with this stuff. Just brushed it on. It was 40 degrees in my garage when I did it so when it dryed you could still see some light brush strokes but in warmer temps it should smooth out like glass. You can also use a roller or spray it on if you have a spray gun.
Also another idea is Rhino Lining. I think you need a special spray gun for this but Im not really shure. The Rhino Lining is much thicker than the Herulining (almost like rubber) & feel it will inulate better from your hot exhaust. I had a friend do this on my old 94 Cherokee & the jeep was much quieter inside. You can also get it in several colors. I think the POR15 comes in different colors also.
I think you should go with the Rhino Lining but there might be many other options out there so use the internet & you might be supprised whats out there. Do your reserch & maby call the company's that make the paint & let them know what you want to use it for & see what they say. Hope this helps you & good luck. Enjoy Hawaii.
Wish I was there dammit!!!!!