After applying filler to bare metal and then primer; can I still work and sand past primer? Would I then need to reapply the primer?
That’s the way it has been done for a hundred years. Well since the beginning of body fillers anyway.
When do you know to stop applying filler and then move to primer? So if I go past the primer sanding into filler I will need to prime again?
You straighten the surface back to its original form using filler ( when you can't get the metal perfect) , primer is for filling sanding scratches & a base for top coats .
Back in High School, our Auto Body Instructor, Mr. Stowers would say, “ There’s only one other part on your body, more sensitive than your hand.”
Once you think you've got everything as smooth and perfect as possible you use a black guide coat sprayed lightly over the body areas, or just some rattle can flat black sprayed from far away and lightly cover the areas. Then go over that with something like 320 grit to see if there are any high or low spots to indicate there's more sanding or filling required. Once it's as smooth as possible shoot a coat of primer, and check it all over again. Then it's ready for paint if it's still smooth as you hoped.
Any minor imperfections will stand out like a sore thumb once paint is applied. Light colours are your friend.
And repeat until you can sand off the guide coat without breaking thru the primer. Then it's ready to seal and paint.
I am going to ask you this again, maybe you will answer this time. What kind of car are you working on? It would sure be far more productive and interesting for the members here helping answer your questions if you had a build thread with pictures showing what you are doing. it could be a thread where you could ask peoples opinions on how to do things rather than having dozens of individual threads asking for help on every possible step of a restoration
?????? No, that's the correct process. But once I do all that I still shoot another coat of primer and give the whole car a light sanding before my paint. I do epoxy sealer over the initial bodywork to seal the bare metal and whatever filler I did. Then I usually end up finding some small areas that need a skim coat after sealer. Once those are all revealed with the guide coat, and fixed, I prime and give the primer a quick, light sanding, and then shoot my paint.
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