Removing rust from the fuel tank

I started a thread on this earlier this year, and the various tank coating products were mentioned by listers. I checked tham out, but found that you need to remove the fuel outlet line with the gauze filter on the inlet, otherwise the liquid coating could seal up the filter. So I have experimented with my replacement (less rusty) s/h fuel tank. I used an Oz product "Kitten Organic Rust Converter" that must be similar to Jenolite, to passify the rust. It does leave a black phosphate coating which I experimented with for some weeks by treating a rusty washer and then soaking in petrol. The coating while softening did not disolve or disintegrate, so I am hoping that any loose material will be caught by an in-line fuel filter which I can visibly check. The s/h tank I got had surface rust in the bottom with most along the bottom seam. After giving the tank a thorough hose out and drying in the sun for a few days, I poured about 50 mils of rust converter into the tank and sloshed it around so that the bottom seam and obvious rusty areas were covered. Than left it for a week to dry out (while I dealt with a bit rust in the boot floor and rear seam). It has been back in Kermit for 2 months now and there is no sign (YET) of any of the black coating turning up in the filter. I shall continue to keep an eye on it and let the list know if any problems occur in future. I am going to drain a bit of fuel from the tank via the drain plug each service to remove any water and this should extend its life. Does anyone else ever do this?