I thought of that, but I don't think they make a product that can be used on plastic. I've used the product that you mentioned years ago, and it worked well on the inside of my metal fuel tank.
It had rusted pretty badly on the inside. After removing as much of the rust I could, I sealed it with Kreem.
Description:
KREEM FUEL TANK LINER is designed for use as a preventive maintenance product in metal tanks new and old; containing gasoline, gasohol, or diesel. KREEM TANK LINER has a unique formulation with extremely rapid set-up that prevents leakage from hairline cracks and seam pinholes by coating the tank’s inner surface with a fuel resistant elastomer.
Not for plastic tanks. KREEM is NOT compatible with all fiberglass tanks. You must spot test before use. Read the Kreem “how to” brochure for detailed application instructions.