I know you said this tank had some dents but I am going to answer to the decal issue. I do alot of motor cycle tanks and stuff and the best remedy I found for the decals that alot of the manufacturers clear over is to sand them out with about 180 untill the decal is gone. then feather edge the paint out really nice. Than prime kind of heavy and block and you should be able to get it nice without using filler. I know this is different than you are doing on this project. But just FYI.

I had a tank come in with dents in it also. I pulled them with a stud gun. I flushed the tank with water and then used a stud gun to pull the dents. Than applied small amounts of filler and primed. I have also seen some tank dents fixed using that crazy paintless dent repair tooling. I am not sure how that all works though.

And don't worry the pros on here do not come here to just flame on people that ask good questions. Its the people that come on here and act the fool that we like to flame.

Keep the questions coming.