I dont think I ever mentioned ATA, if you were referring to me. I agree with Terry that just sanding and polishing may be a better approach. No matter what, its going to be a ton of sanding, trust me.
Cooling lines are in fact a "normal" side effect of vacuumforming. The only way to relieve the issue is to preheat the molds or change the angle of the forming to make the line minimized or make the line somewhere less visible. You can also minimize cooling lines by "pre-streching" the ABS before forming it, like industrial machines do. Its tricky there too. Too much pre-stretch and you create webbing. With ABS its a REAL challenge, no doubt.