Collecting walnuts

One of my hobbies is dabbling in woodworking.  Since I learned that we have black walnut trees, I've wanted to figure out how to harvest the nuts from inside their skins both to retrieve the nuts, but also to try to get the oil out for use as stains.

Last year we harvested walnuts from the yard, but never actually did anything with it.

Now that things have calmed down somewhat, Wifey and I decided to try it again this year.
 
This morning, we took the three kids out on a walnut-collecting expedition.  As we meandered around the woodsline of the orchard we collected what we could from the ground.  We also used a fruit-picker to get some from the trees.

In the end, we collected a decent number to mess around with.  Now we need to sort out how to actually retrieve the nuts and oils from them.