Staining? Is that painting? Edit: I found it on Wiki. To get the grains out…, they usually will come out after your first lair/film (i don’t know the correct word) of wood stain has been put on. You have to sand it after that first lair and put a second lair, sand it again (lightly with a high (180, 220) number sanding paper), then the third and last lair. The gaps can be filled with fluid wood, if they are not too big. Fill the gaps, put a little more then needed in the hole, so that it is a little sphere, because it will sink in when drying. Finish it with a bit more fluid wood (once dry, the next day) if needed or else sand it and stain it.