You can look on my site to see a model green screen that was done on about a $2500 budget by upThink Studios from Atlanta, GA. Of course, you don't need to spend near that much and the lights used were a fraction of that budget. He put the majority into the 'hard cyc' type green screen he constructed.
You can see they followed my common recommendation of lighting in two layers--screen and foreground subject area. Using home depot shop lights with daylight tubes for the majority of the screen lighting, they also used a couple of our 6x55w fluorescent units (CL-655) for foreground lighting. A totally cool lighting setup which won't heat up the studio all that much. Any further smoothing of the output on the screen would best be accomplished by using shoplights with a cracked ice or prismatic panel on the front of them.