hey, as you have found out, obviously catching crappie is easiest during the springtime spawn. they will bite just about anything that you throw at them.
when the water starts to warm up the bite slows down and then you have to really like crappie fishing to catch very many...atleast that has been my experience.
i see more and more people pulling cranks. you can use the same rods for pulling cranks that you do use to pull jigs. however, you'll probably want to use a stiffer rod for pulling cranks if you do it very much as a crankbait will cause a lighter rod to bend a great deal more. the bandit series crank is a good one. also i like the strike king slab master. it just depends on how deep the crappie are suspended. i've had luck with this method trolling with two B'n'M Sam Heaton 9 ft poles from a 10 ft boat equipped only with a trolling motor. it sure helps to have a nice boat outfitted just for crappie fishing but right now i don't have that luxury. you just have to use what you have and then trial and error until you have some success.
i also have had luck in the past 2 weeks fishing deep sections of some local creeks from a canoe. no electronics, no motor. just the sam heaton rods, some jigs, and southern pro baby shad baits under a slip float. when i find a section of the creek that looks promising, drop a small anchor and use vertical jigging and cast and retrieve around structure...and was surprised at the results.