Diffusers would be essential for what you’re trying to do there.
People use all kinds of things for diffusion material, from spun glass cloth, dacron, or silk, to plastic shower curtains, to baker’s oven-proof cooking paper. Be careful if your diffusion materials are not fireproof. While plastic shower curtain will make a nice diffuser, it is easy to melt it or make it catch fire.
Meanwhile, your diffuser, whatever it is, works better the farther in front of the point light source you can place it, because it makes the overall light emitting surface bigger. Right now your actual light source is the tiny 2-3 centimeter coiled wire inside the bulb. That’s what makes the light so directional and harsh. When the same amount of light energy is coming off of a 3×3 foot area, you get a softer more pleasant and even light. So hang the diffusion material a foot or more away from the light and see how it changes the character of the light. I know this clutters up the set with more stands and other bric-a-brac. Which is why I like to say that a professional lighting instrument winds up cheaper and easier to use in the long run than home depot make-do stuff. The more work you do, the more you appreciate the precision control and faster work flow of using real pro lighting gear. Sure, you can make video with MacGyver stuff. But consider it only a stop-gap while you save up for the good stuff. And you can find good stuff used that will serve you for years. My light kit is over 20 years old and still works fine. After 20 years’ amortization, the initial high cost works out to “free”. And I really appreciate the time it has saved and the control it offers.
Another way you can do it besides diffusion is to bounce the lights off of white or silver foil-covered cardboard or foam core boards, but while this makes a superior soft source, you will lose a lot of the energy of the lights in the process, they won’t reach or cover as far. This trick is better saved for lighting talent and not green screens. A better way to go on “cheap” green screens is to use long fluorescent tube lighting instead of halogens. The flo tubes already have a green spike in their spectrum, and the tubes are a softer, more diffuse light source as well.
or… Google “Bill Holshevnikoff” and “foam core soft light” for instructions on how to make a soft box attachment for your halogen light that will work almost as good as a Rifa or Chimera, for less than $10 in materials.