Thanks Jeff. I am hoping to be able to media blast my rear panels at very low psi. I may do the same with my doors if I can't get the grain perfectly clean.
Stop. Like Bob wrote any media will reduce the grain somewhat. More aggressive or higher pressures will do something ( a little or allot) to the grain. I also would chemically strip with some light wire brush ( watch eye and skin protection) work in circular patterns for metal bases panels. Any damage using media blasting will make some to want to add primer will produce other problems.
As far as the "plastic" panels chemical stripping carefully would be my choice also. Number of threads discuss using commercial products made for this as well as lye based oven cleaners. Always test on the back side first
I will have to decide if I am going to do anything with the inside of my doors. I have not cleaned them up yet, but will do so after the outside is cleaned up. FYI there is no rust inside the doors.
Might want to kill any rust on the surface or hiding in panel joints by flushing. You can see what you have and make a choice
Also did the factory use all of that dum/dum sealer inside the door or was it done by whoever restored the car. There are literally pounds of it on the door panels.
There is normally a pass of the sound deadener wand onto the inside surface of the door skin. Not sure where you found the "dum-dum" there is the dark gray stuff on the surface of the interior side of the door that sealed the weather shield to the door you can see in your lower picture
Also it looks like the red oxide was only used on the front fender side of the door and inside the shell. I have not seen any evidence of primer on the rest of the door interior panel
Normally you will find not real coating of the textured surfaces under the original interior color except for what appears to be overspray from doing the other surfaces