According to several wood-bending experts I've talked with over the years, the hot oil does not penetrate the wood enough to matter, and can be cleaned off with a strong solvent like lacquer thinner without affecting the finishing procedure. Never done it my self, just relating what I've been told. I suppose if you used a very poor grade of American walnut with very large, open pores, there could be a problem, but not on tight-grained dense woods like most high-grade stocks are made from.
JR

Be strong, be of good courage.
God bless America, long live the Republic.