Tony gave you some good info.
You can order a product called MoHawk oil grain filler which you can add color tints to the filler also.
I like to apply at least 3 coats of sealer with sanding between coats befor I add any grain filler. This will cut down on the amount of filler needed. When I apply the filler I use a plastic or wood paddle to spread the filler. Long ways 1st then cross grain and remove as mush as posible before it sets. Then I let it set and sand with 220. A coat of sealer is sprayed on this will allow me to see if any areas are not filled. I will repeat if I need too.
I dream a lot. I do more painting when I'm not painting. It's in the subconscious.
::: Andrew Wyeth :::