SJU, PRIME OR NOT TO PRIME??? If you are using acid you should never put polyester products over it. Even fully cured (if you want to call it that or gassed out is the proper term) it will push that ploy off eventually. I have come across some non poly based fillers that can (so they say) go over acid. You need to read the tech sheets or call the product manufacturer if you are in doubt. I would never recommend filler over acid.
I prefer to put filler over bare metal (as troy has said). However, if the project is going to sit bare for more than a day or two (as Centerline mentioned). I use acid then I prime before my filler. I have totally given up on epoxy
after they removed the lead. I don't care what anybody says... It is not the same stuff without it. There are much better ways to go these days.
SJU... I would make a few phone calls to get all the tech info on the products you are using before going forward. They are the people that will write the warranty check if their products fail using their procedures. If you need help with contact names and numbers..PM me anytime.........Good luck...... Bryan