Primers, like paints themselves tend to be a personal thing. Enamel, acrylics or laquers? Automotive or model? The few times I've used resin (I tend to do OOB), I went over the part after the wash stage and located any pinholes (a fact of life with some mfgs) and filled them with an automotive spot'n'fill putty. When that's been cleaned up, I wash again and let the part dry. I then apply several misted coats of primer allowing until I have a good covering w/o loosing the small details. Hope this helps a little