Proponents of chemical stripping seem to always tout that rust and paint will be removed from all the hidden areas that abrasive blasting wouldn't get to. My question has always been, okay, you've taken all the paint from the inaccessible areas, how do you now get to these areas and coat them with at least primer?

Well if the area is in accessible chances are there was never any paint there and why rust exists !!

The thing is, rust never sleeps. By getting rid of it in those areas you now have the opportunity to do something to lessen the chance of it coming back. That can be as simple as spraying the insides of frame rails, etc with WD40 or buying and using a product like Eastwood's "rust encapsulator" which comes with a long tube and spray nozzle to access those areas. And chances are the finished car isn't going to see rain, puddles or snow in the rest of its days - thus minimizing rapid progression of any flash rust that does happen to form.

Its like having a cancerous tumor removed, you don't say "that's it" and go home, you get tested to make sure they got it all and then you take steps to make sure it doesn't come back.

I'm just going on the sales literature for my 1967 GTX that stated the bodies were dipped in primer for 18" from the bottom of the body. I would think that would prime areas that were inaccessible, especially in the quarters and sills.

Correct, that was the whole intention of dipping, to coat everything inaccessible, the only reason for floor/frame and body holes/plugs as well

I'll stick to sand blasting, as I've seen too many cases of chemical stripping/dipping come back to bite you in the final paint, as far as blasting inaccessible areas, I'll do my best to get into every nook and cranny, if I'm doing a floor or trunk or any other area that opens up frame rails or caverns, I'll blast with that component removed to access those areas, then later a primer acid etchant, epoxy primer sealer or other rust preventive measure to coat inside frame rails or other caverns that will be sealed over with body panels, caps, flooring, etc, etc

Do you ever use plastic? Urea plastic to blast paint off outer body panels?

Well it obviously wasn't that great of a dip as evidenced by the number of cars needing floors, quarters, trunks, trunk extensions and frame rails!!!

Well after you did then it's supposed to be E coated. That's supposed to fill all void etc. pricey to dip and E coat. Think I will blast either dry or wet. Will check out all my options. don't mind using a chemical strip for the panels. learning more as I read the pros and cons

I was incorrect, it was only 15", not 18".

If the car was on a rotisserie you could put some over reduced epoxy primer in a squirt or spray bottle and use it to get primer into places where the sun doesn't shine. The bottoms of these cars were full of runs and drips from the oem dip process so recreating those runs would be more authentic than just spraying it with a gun.

Some places you won't be able to reach, but as long as you have primer around the places where the water might get in that would be better than nothing.

The hoods on these cars only have primer overspray dust underneath the bracing. If you turn the hood upside down you can pour watered down primer on the bottom and have a helper help you tilt the hood around to get primer back up where no paint gun can reach. Once it's dried you can feather out any runs and keep going.