Heck of a tip. Thanks. So I was surprised the gasoline with a lot of SeaFoam didn't seem to be working as aggressively as expected. In frustration, I tilted the tank and fired a can of brake cleaner in there straight at the varnish I could see. It did cut it. So I fired in another can and sprayed that all around as far as I could. Then left it in there and sloshed it around whenever I walked by. It seems to be handling the varnish well. But the top of the tank still has those tiny pepper flake sized rust flakes and that's about the top 3/4. So I got some radiator system rust dissolving solution which is safe for plastic parts. I will see if I can loosen and get rid of those flakes by filling the tank half full with hot water and the coolant solution and flipping it upside down on my metal mesh hitch carrier on the LandCruiser and then run errands with it. If that gets rid of the rust flakes, then when I flush it clear I'll be able to see if there is any varnish left and do the Simple Green trick. I already have a gallon bottle sitting out by the bench thanks to your post. Great call - thanks.