The wood finish I do is really easy. I use chalk pastels, I first spray on a light coat of Modelmaster Sand with lacquer thinner so that it dries quickly, I only wait about 5-10 minutes for it to dry. I take different color chalk pastels, like burnt umber and raw sienna(you should experiment with your colors) and scrape them into a powder, don't mix the different colors together, keep them separated. You need a straight,flat,chiseled paint brush like you would use for dry brushing. Dampen the brush with regular water but you don't want the brush"wet" you have to experiment with this,but it's not difficult you will pick it pretty quickly. I use the lighter shade of the pastels first, just take dampened brush and put it into your ground up pastel chalk, you don't want a lot of pastel, little goes a long way. Just drag the brush onto your Sand painted surface in the direction you want your wood's grain to be going, leave a "grain" with your pastel,don't try to completely eclipse the original Sand color. Next take your darker shade and use the same brush stroke,here's where you experiment,you can change the way the grain looks by using the darker shade pastel in variation,lighter here,darker there,lift the brush sometimes instead of dragging it the full length of your"wood" this will give the effect of the way real lumber looks where the grain runs out. When I'm done with the graining I spray a coat of Testors gloss clearover it with lacquer thinner, you can manipulate your gloss by using more or less depending on how glossy you want it to appear. I have used this same technique for do WW I German Fokker aircraft camouflage, works great. You have to experiment,before you clear coat you can also wash the chalk off if you don't like it and re-do it.