Lewisville has flats, have friends that have caught them there, not sure about the population at Whitney. Catch what bait you can from the same body you're fishing, 6-7-8 inch is best but 4 inch sunfish will still catch fish. Green sunfish are more feisty but bluegill works just fine. Use a big ole circle hook, 8/0 9/0 10/0. Rock bank close to a channel is a great place to start.