When I cleaned out my tank, I removed it and shook it around for awhile with some chain in it. This dislodged most of the big stuff. Then I installed a new glass filter under the truck just in line out of the tank. I could then see what gunk was still it the tank. There was a bunch.
After about 4 tank fulls of gas and 4 filter changes, it runs fairly clear. I clean the filter about every oil change now. This, in addition to another glass filter at the carb, seems to work great. Try and keep the tank full and rust wont get much worse.
