Don't sand it down until all the construction is complete. You don't want get your surface smooth only to have it pick up new scratches when you're making that one last cut. I find birch pretty porous so I like to sand it down to 220 grit. I start with 150 Aluminum Oxide, to 220 Aluminum Oxide, and then 220 garnet.

I find BB looks very nice with just an oil wipe-on finish. Tung oil will tone it gold and make the grain pattern pop. Do a search in Craftsman for oil and there lots of info.

Colouring BB can be a bit tricky because it has a tendency to blotch. Sanding it down with 220 garnet helps a bit with even coating as it burnishes the grains. If using oil/gel stain, a coat of conditioner first will help with blotching. Again, Epstein had a post in Craftsman on how to make your own conditioner (or you can just buy it off the rack).

This year, I discovered and fell in love with water-based aniline dye. The colour is deeper, richer and more transparent. Unfortunately you have to go through the extra steps of grain-raising, but for me, I think its worth the effort. To keep this dye from blotching, I first spray the surface lightly with water and wait one minute for it to absorb before applying the dye.

Gar.