There's a lot of guys that say it sucks, like it comes off in sheets inside the tank.
Something about it working like shit with today's fuels. If the tank is pressure tested and you just want to seal it for insurance, I'd skip it all together and run it as is.
That being said, I have used a blue sealer from Eastwood iirc. We bought it to seal the tank of a rat rod we built and had some left over, it really kicked ass. But I put it in a cheapo sporty tank that literally came out the box with 4 holes; we welded em up and sealed it just to be sure.