Filling the grain will be the single most important step you take to get that smooth finish.
I can not stress the importance of this step enough.
That being said, there are a bunch of methods you can use to fill the grain.
Lots of guys use the McFadden grain filler. I have used it myself with decent results.
It takes forever to dry though, and may still shrink afterward.
Lately I have been filling grain using Z-Poxy, which you can buy from LMI.
If you do a search of "Z-Poxy", you can find a semi-informative thread I put together on using it.
Whichever route or product you use, you will need several applications to fully fill the pores.
The pores of Korina are quite large.
You should also find plenty of information on this forum, as this topic has been discussed quite a bit.
Best of luck,
James
Oh yea, shellac goes OVER (after) the grain filler.