Gene,
I dealt with part of your question towards the end of this thread.
http://www.sketchucation.com/forums/scf/viewtopic.php?f=79&t=5929
I have attached a quick example here, in which I have used the standard cherry wood material from SU itself.
Rather than messing around with the material control handles...which can be a little messy if you have many orientations of the material to deal with...I simply painted it onto one surface (in order to load it onto the In Model collection) I then right-clicked the swatch in the In Model browser and exported the material as a jpg to my desktop. Obviously, you don't need to do this if you already have a bunch of wood textures as a starting point.
I then imported the image (as an image, not a texture), stretched it to a good-looking size, then duplicated it and rotated it to all the different angles I needed. I then selected all these and exploded them.
All you then have to do is sample the appropriate one (Paint Tool + Alt) then paint it onto your panel.
I have left hidden geometry showing in order to demonstrate that you can use lines, then hide them, in order to separate different angles of grain on the same flat surface. (Not so much for your benefit as for any passing complete beginner.)
You can achieve the same result by right-clicking any texture and choosing Texture > Position...I just find this way faster and more convenient.
panels.skp
panels.jpg