The Yamamoto Shad Shaped Worm is as good a smallmouth lure as you can find on Powell. Fish it on a drop shot rig. Stick with the dark green, green/white laminate and natural shad colors. Walleyes will hit it, too, if you put one in front of a walleye's nose. The good old Yamamoto Series 40 curly tail grub in watermelon and shad colors works well, too. You can fish it on a jig head or a split shot/light Carolina rig. The Yamamoto Senko is another great lure in the same colors as above. You can fish it weightless, on a jig head, Texas rigged or on a drop shot rig. I also like the Yamamoto Kut Tail worms fished on a drop shot, shakey head and Texas rig. These are the soft plastics I recommend.
In the past when I've seen a lot of surface activity from shad and/or bass I've thrown a Spit 'N Image walking bait with good success. I've also caught both smallmouths and walleyes on a Rattlin' Rapala lipless crank bait in the chrome/blue color.
One thing about fall fishing - be prepared to fish the entire water column from just a few feet to 30-plus feet deep. You might catch fish at all those depths on the same day. Also, for soft plastic fishing be sure to use fluorocarbon line or at least a fluorocarbon leader. In Lake Powell's clear water this can make a big difference as fish are more likely to hit a lure presented on a line they can't see than one they can.
Ed Gerdemann