My AT1 tank was pretty rusty. I used 2 gal of evaporust, it came out nice. I have used vinegar in the past. Used on a rusty DT400 tank and it came out really clean and no flash rusting. Vinegar does a good job of cleaning the rust but usually will leave the metal in a condition where it will flash rust. Just need to keep the tank refilled with gas. 

My experience was good with Metal Rescue and a bag of fish tank rocks from the 99 cent store. You can get a few redos with pouring the used MR solution through and old t-shirt fabric into a container. Fill the tank up almost full with the MR solution, pour in the rocks, put on some good Rumba music and shake dat thang...Blast out with water, dump, and pour some rubbing alcohol to take out the water. Repeat until it looks good. I then took a little 2 stroke oil and some more alcohol and mixed it around the tank to keep it from rusting up again until I was ready to use it.It came out pretty good. I bought a 10 pack of fuel filters on EB and used about 3. I don't see any fine particles anymore after the 3rd one.. TIP..use an old petcock when cleaning then put a new one on when your ready to use it. good luck!

Evaporust for the tank. Keep checking it to see how it's working.

KDI has the air filters.