And one of the "tricks" in motorcycle tank repair is having the rig to hold the tank so that leverage can be used in the PDR process without messing the tank up someplace else.
My limited experience/knowledge on re-bending metal that I learned is to "reverse the hit". IOW's , picture how the hit occured, angles, place of impact, and "reverse it".
So, yep, you begin by working outward in.....as stated , patiently.
I've "saved" stuff from a "totaled" minivan to repairing buggered JIS screw/bolt heads.
tools aren't cheap.