I've had some success tying a black or purple wooly bugger on a 2 ft leader and bouncing it along the bottom with pencil lead. It's just a kind of a variation on the corkies and yarn setup, and you could probably use traditional steelhead flies or nymphs too.
The problem with using a fly under a float is that you have to weigh it heavily to get it to sink unless you're fishing pretty froggy water. With store bought flies you don't always know how much lead is wrapped around the hook. You could put some split-shot on the leader but that creates another hinge in your line that can reduce control. Seems better to use jigs or to tie your own jigs or to tie flies onto jig hooks.

Maybe you need to go out and spend a couple hundred bucks on a vice, lead mold, feathers, bobbins, scissors, etc and tie your own jigs. This, of course, will lead to an interest in fly fishing and you'll soon need to arm yourself with top quality graphite rods in various weights and lengths, along with reels, spare spools, lines, etc.
You can imagine the financial drain you are about to experience. You can save yourself by giving up fishing now. And if you have any Loomis rods I'll be glad to take them off your hands...