And at a later date if you wish to paint the paper that's already on, rather than try and remove wood chip ( that is a pain to remove anyhow) You can buy what is called, " Stain blocker) very much like a normal small tin of white paint, you paint this on the day before you are ready to emulsion, if you don't use this and just paint over with the emulsion, the stain will just keep showing through, as quick as the next day. Two or three coats of stain blocker is a good idea, providing its a smallish area, it would be very expensive to do a whole wall, as its about £10/ £12 for about 750ml.