Fuel tank sealing

[rovermorris999]

The tank on my Daimler E20 is rusty inside, no leaks but some flaky rust which has caused a failure to proceed on two occasions by blocking the pickup pipe. It's definitely this as I've has a look inside with an endoscope. Not a pretty sight.
So time to remove the tank and clean and seal. There seem to be several different suppliers of slosh-type sealants out there, does anyone have first-hand experience of any?
Is it worth having the tank professionally cleaned first? Some of the kits do contain cleaners and surface preparation products but I would imagine a blast with a steam cleaner might be better.
All suggestions gratefully received unless anyone has brand new tank going cheap!

[rovermorris999]

An update: the tank is now out and it doesn't look as bad as I thought. The tank is, like I am often, baffled and from what I can see through the various apertures there is only a little surface rust, mainly staining. The endoscope made it look worse than it was as it was a bit blurry. Quite a few bits of crud in there but what I think stopped the car was a small cardboard disc, the sort you get inside the lid of a screwtop bottle. This was in the area of the pickup and my guess it was sucked onto the end of the pipe and held by the vacuum until I blew back down the pipe from the engine bay to clear it. The bits of loose crud look small enough to pass down the pipe and get picked up by the inline filter I've fitted. Certainly none of them look big enough to block the pipe.
So do I just rinse the tank out, dry and replace and keep my fingers crossed or is it worth getting it cleaned and sealed?
I suppose an alloy tank would be the way to go but not a cheap option but probably the best.

[rovermorris999]

Regarding sealing, the baffles do worry me. I can imagine a big build up of sealer which might come off later. Molasses sounds interesting, tasty and sweet-smelling at least.