Wood – What type of wood is this

Pine is a difficult wood to stain under the best of situations. Pine has areas of different density, color, and resin (pitch) content. Using a product like Minwax prestain helps a bit. Follow the timing instructions carefully when using a pre-treatment. Little tips: i like to apply a liberal coat of oil based stain with a sponge brush. Let it set a few minutes, then rub it in and evenly distribute with a lint free rag. As one rag becomes saturated with stain, I use a second drier rag to finish the rub in. The wetter rag is great for distributing the color. You don't want any really wet stain remaining on your wood after the rub in. Once you get to the urethane, sand lightly between each coat with 220 grit paper to remove any dust bumps. Remove all sanding dust with a slightly damp cloth, let it dry and apply next coat. Again, I prefer a good grade sponge brush, but a good grade regular brush for oil/urethane works good for appling the urethane. Remember, thin coats, and sand between each coat.

Wood fillers for filling grain are very different from those used for structural repairs. Grain fillers are diluted and rubbed into the wood grain. See the attached listing from Constantines, one of the leading woodworking suppliers in the U.S.:

http://www.constantines.com/pastewoodfiller.aspx

They are also a source of components and books on building guitars.

I do not know of a non-U.S. source, but they may ship internationally and their info may help evaluate local resources you find.