My previous truck camper had a metal roof and I put two coats of Henri-Tropic Cool over it. It’s a 100% silicone material that has a lifetime warranty and is 100% waterproof. Did the roof with a roller and 1 gallon which was about $75. Knocked the external roof temperature down by 32 degrees on a hot sunny day and the interior ceiling temps by 16 degrees.
Neil & Yoly
2016 Ram 2500HD Tradesman, 2WD Crew Cab, 6.4L Hemi
2018 Travel Lite 840 SBRX