The graining comb is a two-sided tool. One side produces a coarse grain, the opposite side is finer. Use the one appropriate to the type of wood you are recreating. The finer will produce a tighter grain. To use the tool, drag it through the wet glaze. If you run through several times, you make a subtler, softer effect. A graining roller or rocker is a roller on a handle. To operate you roll it through the wet glaze. Tilt the wrist as you go to alter the grain pattern.
Brushes can be used in wood graining, as well. There are two main kinds. The flogging brush is wide and flat. It has very long bristles. The bristles should be natural hair. Tap it into the wet glaze surface, and it leaves marks that look like the pores of the wood. A stiff chip brush is helpful. Chip brushes are cheap and available at virtually all hardware or paint stores. Drag it evenly through wet glaze to make grain lines.
If you lack access to the specialized tools, try these techniques. Fold burlap into a square. Drag it through wet glaze and the coarse weave will make glaze lines. You can also employ steel wool the same way. Steel wool makes subtle lines since the texture is finer.
You will need some regular painting tools. Plastic containers hold paint and glaze. Don't forget mixing sticks at the house paint store. Drop cloths are essential to protect furnishings. Tape will block off areas you don't want to faux finish and is also useful to hold down drop cloths.