I used original doors since the repro grain was very "unpronounced". Even with the factory grain, I used 50% reduced epoxy to avoid filling the grain, then shot the interior paint (PPG DBC which doesn't build much) in the recoat window so no sanding. Grain ended up very visible.
I was really concerned about the actual interior part not so much the jamb area as I figured the single stage in the jamb area was going to fill the grain anyway. Not sure how you avoid that. In my case, I had rust repair in that area so not only wasn't I concerned too much about preserving the grain, I actually preferred it was obscured making my patches disappear.
I guess this answer doesn't help much. Some pictures that show why I didn't want the grain preserved, and some pictures of reduced epoxy with DBC over it.