Word of advice? Yeah, leave that to the pros. Chemical milling, aka "acid dipping" was popular in the early days of ProStock as many know but what some may not know is thatcontrolling the rate of milling is very tricky, the chemicals are dangerous & most likely doing it in your garage/backyard is illegal.
"Big Willie" Robinson lost a Daytona body, it was eaten so badly. There's plenty of stories where bodies-in-white were dipped only to have a roof panel come out of the tank---and these were done by pros!
A friend that worked for Penske in his Trans-Am days tells of cars being so thin they had to spray foam insulation on the panels so they wouldn't flex or cave-in at speed. He claimed without the foam you could shine a light behind a panel & see the glow from the flashlight. Look at some old P/S cars & you may find foam sprayed to the inside of doors, quarterpanels, roofs, etc. There's a reason for it! IIRC, the famous "wire car" of Don Carlton was "wired" just for this very reason.
The old S/S Darts & 'Cudas had their doors dipped & you'll find some weren't as cleaned up after dipping resulting in continued erosion from the acid.