These boards came from our 1895 cellar.
They are wide, "old growth", tongue-in-grove pine.
If they came from Texas we would call it ship lap.
We want to use it in back of our TV nook.
We wanted the wood white, but still be able to see some of the character.
And I have tried commercial white stain,
and it is pitiful.
First, plan on doing this outside, it is messy!
Mix a 1:3 white paint to water ratio.
Flat or satin paint works best.
Try a "test" board piece and let it dry completely before committing to painting a bunch.
Apply pretty liberally to all bare wood.
It will looks a bit messy like above.
Then go back over the entire piece from left to right in one continuous,
straight stroke -- until you finish the entire board again.
So after going over the boards with the continuous strokes,
they will look like the above boards.
And heads up,
the boards will continue to absorb the paint for awhile.
That is why you need to do a test board.
If you want it more opaque you could add more white paint to the mix.
For more transparent, the options are:
adding more water / wiping wet off excess with a rag /
lightly sanding after your board is dry.