mon,
as slow as you can with the current. If you travel against the current you'll halve the strike rate, flathead sit on the bottom facing the flow.
I got best results in a 12footer with a 15hp at idle basically just guiding the the boat along the dropoffs or with an electric doing the same. You want the lure chewing the bottom ever metre of so & a good crisp action rod so you can see it working.
cheers,
chris
PS THINK PINK, PINK PINK