Tank liner traditionally is a simple quart of 100% Urethane pure and simple.
Now with these asshats at POR and DR Radiator etc... etc... the prices are fekkin RIDICULOUS!
It should take no more than a quart to do it with 2 hours prep time and Cost less than $20 bucks for the sealer, but you can't even get a HALF pint of anything made by POR for less than $30 bucks.
Anyhow, you simply need some 1/4" or 5/16" chain about a 5 footer or so then put it in your DRY tank and shake the piss out of it.
Then you should rinse it out with M.E.K (which is a slower evaporating form of Acetone) or Acetone because it leaves very little residue, then once it's fully dry, you pour in the sealer, and twist and turn the fuel tank until the entire inside is coated, then pour the excess back into the sealer can you got it from.
Allow 24 hours to dry then re-install and use.