Agreed here Trevor,, What you are describing is a very well established technique. There are other techniques as well but they all take practice. I have done very little of it in the last 10 years and getting back into it and finding my skills to be rather lacking or pardon the pun,, Rusty.
Practice practice practice.
I have seen some other promising tech as well in some body shop trade papers and will try and sign up for some classes this winter. Plus a lot of youtube videos to watch. I saw some material a while back on shrinking and using these flapper wheels that seemed promising. Amazing results in the demos I saw.
I have a stud gun welder and puller setup. It uses copper coated nails (not real nails, these are specially made) and you spot weld them onto the metal and then use a slide hammer and T handle pullers to pull the dents. (You can often avoid having to cut out the bottoms of a tank)
But indiscriminate yanking will just further distort the metal,, I use techniques with a torch while pulling the dents much like you describe which often makes it a 2 person job.
Much like this setup, (I found the gripper on the puller lacking and modified mine with a small pair of vice grips/mole grips)
See:
https://www.amazon.com/BRAND-WELDER-SLIDE-HAMMER-REPAIR/dp/B00IDYQWK2I know these pictures are a deviation from the topic at hand but the relevance is metal distortion and stretching related to that tank. (My opinion is somebody made that tank, not distorted, but the mystery is WHO? BSA or aftermarket?)
But whatta you guys think? Will this buff out? Believe it or not it WILL.. This car will never be a restoration (Too far gone to be viable) but it IS excellent ratrod material.
It will see the road again, but the body will be mounted on a late model Ford AWD Exploder with V8,. Think Mad Max Thunder road styling. But yes, even metal like this can be repaired,
Funny story on this one (I have 3 prewar coupes). This belonged to a museum volunteer who lives ironically just across the river from me. He owns an extensive collection of vehicles (40 at last count) and while clearing land on his farm found in the undergrowth he actually owned 1 more than he knew about. Fun stuff.