try putting some whole linseed in a coffee grinder-grind em up-add some boiling water-allow to cool a bit then pack his feet with the resulting goo as you would with a poultice. It works a treat. You will have to do it a few times to get good results but its cheap and 100% natural. Mairi.
IMO I wouldn`t use the hoof oil on your horses feet if they are brittle as it could dry them out more as it keeps moisture out. Try the advice above, that sounds good.