To have proper lure action, I stretch the lead length 40 to 50 feet more than usual. The reason is that the longer the lead, the slower the lure moves. I do know that there are always fish there some place, but the trick is the current. I have a speed sensor that goes down on the downrigger to help me sort out which direction the current is running, and I always troll somewhat into the current with much better action. To do this, stay at the same boat speed, watch your downrigger cable angle.
Fish face into the current looking for an easy meal to drift by.
Usually, it is best to guess as to how much line to let out. You can develop, with some work, a graph that tells all, each size needs to be tested. Set up your slip sinker, say 100 feet of lead, now troll to shallow water, watch for the weight to contact bottom. When it does, you know how deep the lure is. The very low water conditions also meant that water clarity was as good as it gets, better than 10 feet of visibility to the angler surely meant that the fish could see twice that.