Welcome aboard! I agree the Auto Pilot/I-pilot MinnKota trolling motor will be money well spent for crappie fishing as well as stripers. So many ways this motor and addons take a lot of the "work" out of fishing. I haven't fished Hartwell myself yet, but can see a trip up there coming soon.
Longline trolling, pushing (spider-rigging slow trolling off the front), and dock shooting are all very effective methods. Some folks do better all year at certain ways and some folks switch up during different times of year. Since you already fish for stripers and have a large bait tank, you probably would do very good at pushing. A simple rig is to use a #2 lightwire hook tied on 18" leader of 6# that is tied to a small swivel. The other end of the swivel is then tied to your main line after adding a 1/2 oz barrel weight to the main line. You can add a small bead to the main line to protect the knot if you like. Use a large minnow on the #2 hook and hover over structure holding fish while trying to keep your bait close to the structure. Use the trolling motor to "creep" around to other structure or to catch suspended fish too. You can substitute the #2 hook for a jig of your color choice and still add the minnow. You can also add a 2nd hook/bait above the barrel weight using a loop knot to increase bait presentation and cover more water. Use those rodholders you already have and just adjust the left/right to spread out the rods to avoid tangles and cover more water.
There are some great rod holder/rack systems available from Hi-Tek that can be used for pushing or longline trolling. Longer rods help with covering more water and avoiding tangles. Check out the B'n'M Pro Staff trolling rods. I use everything from 16' to 8' and in between depending on what the presentation is.
Lot of much better crappie fishermen on here than I am, and I am sure they will be happy to help you out. Use the "search" function in the blue toolbar in the upper part of the page and you can spend hours reading up on different ways including pulling crank baits! Good luck and look forward to you posting some reports of what did or didn't work and ofcourse some pics too.
Slab Masters Tournament Trail ............... www.slabmasterstournamenttrail.net