I wipe on the dye on the outside. For some woods, you can apply one colour and then sand much of that off and apply a second colour on top etc. Other woods act like a sponge and suck up the dye clear through. It's also a bit of trial and error to get the concentration of the dye right so that it doesn't darken too much. Better to err on the side of caution and use a second coat if necessary. At least that's my experience. For the inside I pour some inside and slosh it around to get all of the surface covered. I've also been thinking about getting a cheap airbrush and trying that out.