<VV> fuel tank cleansing

[cfm]

Hi guys:
I decided to follow the POR-15 method of gas tank cleaning, etching and painting (inside). I did the first dtep, cleaning it for 24hrs with Marine Clean, turning the tank, etc. etc. and the stuff really did wonders. However, I was being skimpy and only bought one quart of the Marine Clean, thus only able to flush once. Upon inspecting the tank, I still have visible surface rust, but its nothing like the "crunchy" rust that was in there prior to using Marine Clean.  I have this inclination to "rinse and repeat" this first step, but am out of Marine Clean, and hate to wait and spend more money if I don't have too. The instructions, although good, are not great, and the lead me to believe that the Marine Clean is to remove sludge, varnish, etc and not necessarily make all the rust go away. I want to move on the etching (metal ready) but am unclear just how "clean" the inside of the tank should be. I would assume that the paint (the third step) actually encapsulates the
 irregular surfaces and creates the "blanket" effect that POR is known for in general.
Comments, suggestions?
always appreciated!
Chris Mann
69 monza vert 110/pg
69 monza coupe 140/4