I have some doors and millwork in white oak and have noticed that after we prime it, there are, here and there long thin crevices where the oak had some exceptionally deep grain and the oil-based primer just soaks into the crack and disappears, leaving a thin crevice.
There seems to be three possibilities in dealing with these crevices:
sand the primer off near the crevices, fill with wood filler, and re-prime locally
keep adding primer, sanding and drying, and try to fill the crevice up with primer
move on to the painting stage and hope that the two coats of paint will fill the crevices
Which strategy should I use? Or is there a better strategy altogether?