prime right over the blasted area, but hurry before it turns brown. use a good epoxy primer, it will fill in the sand "pits" and adhesion will be awesome! other blasting media, such as soda may not leave it as rough as sand, and may require "scratching". i prefer sand. but never sandblast the open areas of exterior skins. i like to strip the skins chemically.
DO NOT touch the metal with greasy paws.The oils from your hands will transfer onto the metal instantly.You might want to clean the bare metal first.Just a precaution for contaminents.Adhesion is definitely the key.