Hey David, I once lived in the heart of Northern California's walnut country. English walnuts will fall from the hull to the ground, where as, black walnuts will retain their hull and are difficult to separate the hull and crack the shell. Fair warning... Start your harvest early where squirrels and jays are present or they're likely to do the entire harvest for you! The large companies collect English walnuts pretty early, while only 7-10% have naturally fallen off the tree. They use heavy machinery to shake the trees till most of the nuts fall off. They also have machinery that separates the hulls, as some of the hulls stay attached to the semipremature walnuts. I tend to wait for them to drop 20 - 30% and use a long piece of pvc or a stick with a crutch to shake individual branches till the nuts fall down. Get creative! Also, you can get a nut roller if you'll be doing a lot of collecting. A leaf rake works pretty well too.. They are both great and save the back! Walnuts are much more palatable once dried! Around here I just sun dry them for a week on screens or on the ground... anywhere in full sun... be sure critters can't get at them and don't forget about them if it's going to rain! On the off chance that it's not feasible to dry them outdoors, I keep them in old perforated onion sacks, burlap,
cardboard boxes, baskets... anything breathable, at a safe distance from my
wood stove or in the driest critter free location in my home. The trick is to dry not cook them! Stir them every few days for the first week or two. Check them often by cracking one open to see if the nut skin is crunchy. Once they are dried I put them in plastic 55 gallon buckets and shell them as needed. I've seen under dried walnuts but, I've never seen an over dried walnut... I'm sure it's possible. They're best after about a month after they're dry. Great timing for a fancy thanksgiving treat.
Good luck and happy harvest!