thats hard to say with out actually seeing how the cans are laying out paint.
essentially, you are going to play by ear(eye?). you are going to try to lay it even, with minimal overlap, just enough to evenly lay a wet pass that leaves no line. you want i wet sheen to it while its still wet, that allows it to self level, but without runs.
i have better results spraying down at the material, allowing gravity to work for me, and not against me causing sags. this would be kind of difficult on a cylindrical tank, but still possible. you could make up a rig to allow you to rotate. but you will have to spray a section(1/3?) and wait for it to set, then rotate and spray another 1/3. not necessary, just ideas.
get it on thick, and if you get a run or two, that stuff can be taken care of later with some wet sanding. i bet no matter what, it will look good in the end.
like i said, im just throwin ideas out there, and explaining what i would do personally. if you are truly worried, hire it out, and dont worry.