I have a brownstone house and my exterior door frame which has great detailing to it was painted over the years. We began to strip the paint from the frame, but as we got down to the bottom of the frame, we noticed that the wood is a little damaged and needs to be filled. Since I now want to stain the frame in a red mahogany stain, what type of filler should I use on the frame so that the stain penetrates. Other than this small section, the frame is remarkably great. The wood seems to be oak. What do you suggest we do to conceal the flaws and to insure that the stain absorbs into the wood?