When it comes to installing a fuel tank liner, surface preparation is the key to proper adhesion. While the kits do work, this method has proven to work better and more easily giving more room for error.
I got my phosphoric acid here: https://www.dudadiesel.com/choose_item.php?id=FGphos
Denatured alcohol can be found at your local hardware store and dry gas can be substituted for isopropyl.