Cleaning rust pits / road rash from paint

[napa68]

I am working on the 68 Camaro I just bought back. The bottom of the car is most all original paint (this is an LA car). I am guessing where the rust accumulation is where paint was very light if not non existent. As pictured, there is also road rash in spots that I'd like to improve on.

I have tried buffing compound with a couple of different pads and had a minor improvement. I feel it could be better.

These are a couple of pics where I have not touched anything....



Here is where I have been buffing....




I saw this video a while back and at the 5:19 mark, they speak of using an acid solution that naturalizes the rust in those pits. Has anyone does this and what is the magic brew?



Any other suggestions? I'm all ears.

In advance, thanks!
Tim