Hi Guys
I'm new to this forum and need some help with a problem I'm having with an overall base coat / clear coat paint job I'm doing on a 64 Plymouth Valiant. I'm an old guy (70) and have been working on cars for about 50 yrs and this is my second overall paint job with bc/cc, the first one turned out great. The problem is with the base coat, I have some severe dry spray over the whole car and couldn't figure the problem out until this morning when I discovered that part of the 2nd and all of the 3rd coat of base were under reduced, evidently I misread the mixing cup I was using (old guy mistake). My plan is to fix it by sanding the whole car and adding at least one more coat of base and need suggestions on what grit paper to use, wet or dry, Da or hand, etc. Years ago when I used laquer all the time I'd wet sand with 600 grit and respray or polish so I tried some 600 grit wet and it loaded the paper up pretty fast, this is not gonna be fun. Paint particulars are: Nason Ful Base White in color, 441-21 medium reducer at 2:1, Devilbiss gti gun 1.4 mm fluid nozzle air temp 75 degrees, 20 psi at the gun and I have a 5 hp compressor on a 60 gal tank. any help or suggestions would be greatly appreciated especially if anybody can come up with a way to fix it that's easier than my plan,
Thanks
Bob

Unfortunately there is a huge difference between the old acrylic paints and modern basecoats, even though they are both modified acrylic copolymers.

Basecoats tend to remain kind of soft and plasticky, which explains your paper loading up. The longer you leave it the more it will harden, but do you have that long?

Bad news is that you will have to sand it all down and re-apply. No need to remove completely, but certainly get the surface smooth. A coat of epoxy or 2K surfacer will help with adhesion for your new base.

P500 on an air DA sander with interface pad should rip most of it off but you'll need to do some by hand - P600 dry or P800 wet.

If that GTi has a conventional or RP aircap then you won't be doing yourself any favours at 20psi. Even HVLP responds to a little more air pressure.

yep Chris is right. if you can let it set for 4-5 days or better a week if you can then try the sanding.
Jay D .