You need to post this in the Ohio River forum, I'll ask one of the OGF guys to move it. Markland pool is a big pool, I think I have been talking to you via e-mail, looked at your profile, many of us fish that pool mainly out of Tanners creek, I plan on being down there this weekend to do some fishing and catching..........Doc
Yes, a good pool, the whole thing, doesn't matter. Sometimes you catch, sometimes you don't. Seems like more fish are caught upstream of Cinti, but that comes & goes too. A boat is almost a necessity, then just trust your electronics. Find drop offs & channel edges and watch for fish archs near the bottom.
I for one use only a couple of different baits, live Shad, dead Shad and Skipjack, Live Shad I get the biggest I can find, dead Shad I really like the heads, the bigger the better, Lynn likes to use the body sections, lately they have been hammering the cutbait, Skipjack when you can get it is a prime bait for Flatheads but Blues love the stuff. As MrFish said target the channel edges,dropoffs, tributary mouths, both inside and outside bends of the river, deep holes with structure in them, anything that is irregular on the bottom, wood structure, snags and old stumps right up next to the shoreline.............Doc
Doc and Mr. fishohio have it right on the structure, the only thing I might add is that unless you stock up on shad/skipjack when you have them and freeze some to take on your next outing, you can get stuck, you read this forum enough and you'll hear guys grumbling about not being able to get bait . My point is that it helps to carry some backup bait in case you can't get fresh shad or skippies when you head out. My favs are chicken liver and shrimp, followed by live goldfish and bluegills. Some of the guys don't like the liver because it can get messy but I've caught some nice channels on it, also catch a lot of hybrids with it. You won't get any flatheads with either the liver or shrimp but I've caught blues up to 15 lbs with the shrimp and lots of channels over 10 lbs with both. The flats munch on the gills and goldfish.
As the others have said your best bet is to get either shad or skippies.