Crayfish are an amazingly diverse group. There are about 400 species of crayfish in NA alone. There are many species that won't do well in a pond, because of diffrences in habitat and fish predation. Some crayfish need moving water, others need mud to burrow in and some only live in caves.
http://crayfish.byu.edu/photo.htm this is a great website, lots of pics and info.
If I were you I would do one of two things.
A. Find a supplier of crayfish, who knows which type of crayfish they have, and then double check the habitat preferences for that species. If they match your pond get as many as you want.
B. Find a natrual body of water that closely matches your pond in substrate, depth and fish. And then trap as many crayfish from there as you want. Don't worry about getting all of one species, diffrent crayfish will use diffrent parts of your pond.
On fencing and feeding...
I would introduce the crayfish into your pond at night near or in cover. I have heard of using chunked up bales of straw to cover crayfish. If you put them in deep enough water the racoons will never have a chance.
Crayfish reproduce at least once a year and have many offspring, because they have short life spans (just a couple years) they need to have a high reproductive rate.
Crayfish eat anything they can tear into small enough chunks to eat. This includes vegatation, fish, and each other. At my job we have a crayfish tank that also is used to store feeder fish, ussally small chubs from the bait shop. The crayfish will catch them by the tail and start eating.
One word of caution, do not stock Rusty Crayfish in your pond. They are an invasive species from the southern Ohio area. There is a thread on it.
If you stock enough of a suitibale species of crayfish you should get a good population going with out any extra work.
