Probably not in time for your tourney but anyways.
Fresh cut fish is far and away going to be your most consistent bait. Forget the rotten stuff and novelties. You can run a siene thru the milk to get goldeye and plains minnow. You could also buy creek chubs at the bait shop and ice them. They key to catching lots of cats is to fish hard and fast, especially on a small river like the Milk. Concentrate on the deeper holes and don't overlook riffles. I typically use a basic bottom rig (lindy rig to a walleye man) but will also use drift rigs with floats or just split shot.
If cats are in a hole you usually will have action in minutes. Don't stay in one spot for more than 20 or 30 minutes unless you are still catching fish. I would float long sections of river with a canoe or small flatbottom. Just have your buddy bring his truck to drop off at the end of your run. I have fished cats a lot on the smaller rivers in eastern SD and have been very successful this these techniques.
