Roger -- How are you planning on filling the pores? If you're going to fill the pores with the finish, that will require several coats and sanding between coats to level the surface as you go. Or, you could wet sand with your finish of choice (or a compatible finish) and allow the sanding slurry to fill the pores. Or, you can use a commercial pore filler.
My preference is to wet sand with walnut oil. The oil and sanding slurry will quickly fill the pores. After the oil has cured sufficiently, which can take several days, you can sand back to bare wood (the pores will remain filled) and apply a compatible finish over the top. My preference is a brushing lacquer, like Deft.
Another option would be to use Deft for wet sanding. That's quicker. I just don't like the fumes.