We just finished texturing our ceilings with a knock-down texture, however the following day we noticed wide grid-lines in the ceiling everywhere we taped and mudded. We did not prime/seal the sheetrock before texturing (wish we had), but plan to do it now. Will primer and paint cover these grids?
Paint will only cover up VERY minor imperfections, like pinholes in a wall (and even then, if it's a big pinhole, it may still show through). If texturing didn't cover it, paint (which is MUCH thinner) definitely won't.