normally 2k primer is 5-1 with activator + 10 percent thinners


basecoat paint is 2-1 thinners

laquer 2-1 activator + 10 percent thinners


id get the panel gound down as much as poss in the rough areas treat then fill if ya want to if not load it up with primer to flat back for a good finish

all depends on how far your wanting to go m8

personally id cut the rust out and replace but a bit of surface can be sorted if done well

make sure you key the whole area off properly and panel wipe it to remove silicones etc etc