I did the redkote on my 300 Utility. The preparation is the hard part. Getting the tank out was hard. I used some sort of acid that I had accumulated at an auction to eat the rust flakes. It had no label, but the other stuff around it at the time led me to believe it may have something to do with cleaning concrete- so maybe muriatic.. I had dipped some rusty cast iron in it one time, and it ate that rust away and left the iron halfway bright. So, I sloshed a couple of cups of it around it that tank and gave it time to work, then dumped it out.
Then, I risned it out with water a couple of times. After that, like the redkote instructions say, I sloshed about a pint of acetone around in the tank to clean things further and to dispel the water. Dumped that out and poured the rest of the acetone in the tank and sloshed it around for a minute. Poured it out and let the tank set with the valve port downwards to ensure everything drained out.
THen, did poured in enough Redkote to coat the tank innards, sealed the filler neck, plugged the valve port with a pipe plug to protect the pipe threads, and rolled and rotated that tank for about 10 minutes to give that thick liquid a chance to coat every nook and cranny. THen I unplugged the valve port and drained the excess coating.
When I was done and satisfied, I ran a pipe tap up into the valve port to clean the redkote from the pipe threads, and it was finished.
Have had no rust problems since.....