As a product photographer, I use diffusion panels almost daily. I prefer the flexability and control I get from them over softboxes, and they're easy to store or pack flat for taking on location. Several companies have prefab "blades" intended for holding diffusion materials and fit nicely into grip heads/knuckles, but at nearly $100 a pop, buying several of them may not fit into everyone's budget. A friend showed me an easy way of making my own for a fraction of the cost, so I put together this video to show you the process.
Note: In the video I used a portion of Rosco #3008 diffusion material from a roll I had in the studio. This material is also available in pre-cut sheets for a few dollars each if you don't want to pony up for an entire roll.