There are two very good walnut trees in our field and I would like to propagate them. As far as I know is grafting of walnuts very difficult and requires special skills (which I do not have). So what about cuttings?
Michael Dirr's Reference Manual for Woody Plant Propagation states that cuttings taken from older trees do not root well. He suggests that, "Anyone wildly interested in black walnut propagation should see The Plant Propagator 18(3): 4-8 (1972).
My parents bought a house in Oregan a few years ago, there are 2 walnut teas in frunt. In the past three years they have been digging up masses of baby walnut trees from the shaddy mulch under the 2 trees, the walnuts got barried under the walnut tees years ago and apperantly it takes some time to sprout. If grafting don't work you could try the old fashion way.