how to empty gas tank

[1034am]

I think I'm ready to try the apple cider vinegar.  I did a Rustoleum phosphorus acid treatment twice, first w/water dilution and second time straight and it's still not right. There's a consistent, thin layer of rust though out the tank.
Has anyone had first hand experience w/successfully removing rust from the inside of a tank?

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[1034am]

So, 3 rust remover procedures and i finally have a rust free tank! (first was phosphorus diluted, second was straight, and third was Metal Rescue from home depot.)  Having a sunny day to dry out the tank is the best help in getting it empty.

New problem: something like sand is rolling around in there. going to try a small hose connected to the vacuum and see how that goes. And inline external gas filter, just in case.

[The Buddha]

Phosphoric acid turns rust into Iron phosphate. It coats the walls and sorta makes a scale type deposit. It is a grey/black powder. You have to get that crap out mostly.
You use something like Jasco prep and primer
I don't like the way it works. However it promotes adhesion of paint.

So I first treat the tank with hydrochloric acid. That eats up and removes the rust. Then neutralize it with baking soda. Make a few passes. You really want no acid in there. You also have to work on it with very very hot water. It has to be so hot that as you drain it, it dries up.

Then you put a very very little phosphoric acid with lots of water. That would prep and etch it. Then you can do POR 15 etc.

Prep is the key. Miss that and you'd either have rust under it, or have the coating come loose etc etc. POR 15 likes water, so its OK to put it on a wettish surface, except it should be 100% rust free.

Cool.
Buddha.

[1034am]

Looking for any opinions here: I got the inside of the tank de-rusted, it has some sort of gray coating which is supposed to be gas-safe. A friend of mine (HD rider, but let's not hold that against him!) suggested an epoxy sealant to prevent future rust. Amazon sells a kit for just that.
My concern, is in the future, if rust develops beneath the epoxy, or if the epoxy fails, will it be impossible to reverse? Epoxy company says 'no, it will be the last coating you need', but of course they would say that.

Has anyone heard of experiences w/epoxy coated tanks?