Years back, I heard about some trick you could use to prepare knotty pine before painting such that after the paint dried, you could wipe the paint off from the knots, and what you would be left with is painted wood, except where there were knots, where the wood was unpainted.

This sounds like something I would like to try, but all the Google machine reveals is ways to cover the knots so they won't bleed through, not ways to reveal them.

Does anyone know how this is done? Maybe put wax over the knots before painting? Or do the knots repel the paint so effectively that it wipes off without any pre-treatment?

Thanks in advance for any suggestions.

J