Dale:
I have a few version for the 27F, but basically I would suggest you remove any Matrix and Colour Correction you have dialed in. You can do thsi by simply recalling the factory preset. Then either turn off or reduce any detail enhancement. This will permit best seperation of the indivudual RGB channels and permit a cleaner key. Sometimes it helps to turn on Colour Colour correction and boost the saturation of either Blue or Green as appropriate. Use a vectorscope to ensure you match the colour correction vector boost with the light / paint you use.
Good luck!
Steve Mahrer (Panasonic Broadcast)