I bought a gallon of Berryman Chem-dip. As the name implies, you are supposed to dip your parts in it. Of course I had nothing big enough to dip a 4bbl manifold in and if I did it would take more than a gallon. So I brushed it on and kept it wet for an hour or so. It helped some but it's still not like new. But it will do for a driver.
I got the manifold on and am almost ready to install the engine.