The best way to locate the schools is to troll several jigs in different colors and at different depths until you start catching fish. Then you can change all your rods to that depth and color. Some fishermen have rigged their boats with rod holders to enable them to troll up to 14 lines at once. You can troll a double jig rig on each line and that gives you 28 baits in the water for the fish to choose from.
Boats rigged for this kind of trolling are called spider rigs because of all the rod "legs." A board across the back of the boat keeps up to six rods spaced apart evenly. Three or four more up each side, with longer and longer rods as you move toward the front of the boat, spread jigs over a wide path. Crappie don't have a chance!
A good way to mount a board across the back of your boat is to attach it to the cleats. You can remove it when not needed. Rod holders attach to the board and do not mar the boat. A 2X4 with a pad on each end to protect the boat finish works well. A hook through the board to hold the cleat, with a washer and wing nut to tighten it down, makes a secure rig. There are as many different rigs as there are fishermen. Make one that works for you or copy one that you see.
You should troll for crappie with light line. Two to six pound line works well. Light line allows your jig to sink to the depth you want to fish. Light line also allows you to break off a bass, hybrid, catfish or other big fish that could tangle your line. That is hard to do but most trollers break them off fast rather than tangle lines from 16 rods beyond repair. That can run a whole fishing day.
With all the lines in the water, you would think the crappie would tangle them up when you caught one. This hardly ever happens. Keeping the boat moving as you reel in the fish helps.
If you use this rig, remember to vary your speed. That can control the depth as well as offer different speeds of movement. When you catch several fish at once, mark that spot and circle back - at the same speed.
You can also troll live minnows if you hook them through the lips. They, like the jigs, can be dropped under a cork for extremely slow trolling or can be trolled on a flat line with a split shot in front of them. You can also hook a shiner through the lips on on a jig head and troll them just like the jig.
You can quickly catch a limit of crappie (30 per fishermen on most Georgia lakes) like this. Just don't be greedy, the game wardens know the fish are hitting and will be watching. They will take the fish away if you are over the limit as well as giving you a ticket. It's not worth it. Catch your limit and go home!