I've never trolled crank baits, only jig heads with plastics threaded on. As far as how far behind, I just cast them out as far as I can and call it good. I do catch a variety of fish on them, it's not just the panfish that bite them.
For the stained water, try using a bait that has a lot of flutter, like a curly tail or spinner head; something to make a bit of a fuss that they can sense rather than simply see. The Bobby Garland Stroll'r and Swimm'r have worked well recently, as well as the Southern Pro 2" curly tail grub. But most any brand should provide the same actions.
Yes, I was talking to myself; sometimes even I have to ask for expert advice.