He wants a gradient shader, I believe. As in a texture on the object easier than drawing his own gradient. I don't use HWA so I wouldn't know how to use shaders, and I know nothing about how to use Overlay Redux.
Off the top of my head I don't think this is possible. I've achieved a similar effect using an object as a shader, but it only adds colour to black objects. Until MMF gets masking capabilities I think you're stuck.