i would advise against drybrushing a blucky - i would use washes or woodstains instead - it will give you more of a natural look that i think you are going for
but as for drybrushing in general...its one of the most versatile yet simplest paint applications there is - pick a basecoat....either light or dark whichever you want - then pick a color oppostite to what your basecoat was as far as light/dark goes - dark basecoat=light drybrush.... light basecoat=dark drybrush
either work well - i know over at terror syndicate, steve likes to use a black basecoat and white/cream for the drybrush color
i prefer a dark brown/black with a light grey drybrush - but then i usually put a dark wash over top so that its not so stark
as for the actual technique of applying...just paint your basecoat on first normally - cover everything...
then either wash out that brush and make sure its COMPLETELY dry or i prefer to just get another one - usually something like a 2 inch house painting brush unless its a really small wood trim or somethin - and even up to a 4 if its a large area - take the new "dry" brush and just get a little paint on the end of it - have a scrap piece of wood beside you to wipe the brush on - getting most of the paint off - when the brush is no longer wet from the paint and there isn't much paint going on to your scrap piece - its time to start on the basecoat you layed down
this is the only somewhat difficult part - you have to sweep the brush accross the basecoat with enough pressure to allow some of the paint to come off, but not too hard that it makes a large mark of paint - whatever this pressure is for you, you have to continue using that pressure on the rest of your piece - when you see that theres not much paint coming off, you can dip it back in, making sure to get the excess off on the sreap piece - most of the time i just refill my brush using the scrap piece tapping it on
drybrushing is great and will work for your application, but sometimes its not the best choice - you cant really drybruch a wall or something - usually in strips no more than a foot is about the max i would go - anything larger and it will look fake - this is because we are human and cant keep the "grain" going all in the same direction for much more than a few brush widths
another good aplication of drybrushing is for shading - say you have a panel painted to look like large rocks that are grey - well use black as your dry brush color and use the technique like hatching and crosshatching - for anyone who doesn't know what that is, its when many short lines are places together to form a value - the closer together, the darker the value - its a pen and ink technique - - so using that same idea - the darker you want an area to be, the more you dry brush over top of that area - only instead of always going in one direction, use a crosshatch technique and go over the same area at different angles so that it looks natural and not man made
hope this helped a bit - have any questions feel free to ask - ill try to help as much as i can
riley