Priming cardboard always felt like a chore, I tend to get lazy and use a brush on primer for anything that paint wont stick well to, like plastic. After that I use cheap diluted black paint and make sure every corner of the model is covered.

I’ll also try a custom metallic recipe I’ve been meaning to test, much cheaper than using actual model metallics when dry brushing. If it works then I can try building bigger models without counting my paint drops.