I haven't had a ferret torn up yet. I use the net that goes round big hay bales, it slows the rats up enough to get a good whacking in! Its the only kind of ferreting that I invite other people along, the more people you have standing around, the less rats you lose.
I cant keep dogs for various reasons, but I have worked with terriers and even lurchers, they all enjoy it!
I am yet to use a shotgun, but would use a .410 if anything.