Not much more needed. We mooch as much as we fish the down riggers. Seems like a lost art down here but that is the way I always did it in SE alaska and I catch more than on the down riggers. Also gives some excitement if you have people that dont have patience because you get a lot of bottom fish to break up the slowness of rigger fishing.
The main thing you need to know is how to cut herring. I like the westport style. Seems to give me a tighter spin and is faster to rig. People will say you need a slow looping spin for kings adn fast for silvers blah blah blah. All I have to say is B.S. Faster the better. Look it up on line will probably give you a better idea how it is done rather than me attempting ot explained the setup and angle to cut bait.
We fish mainly in 75 to 125 even out to 150 ft. Some good spots around that will work better than on the riggers. Just about all I do in the canal but in the main sound I use both. Follow the bait, find the fish. Good luck.