When your shooting film (C41 color neg) you really don't need to have those hokey diffusers on your flash. Try over exposing your film (iso 800 at 400 etc.) and set your flash for -1/4 or -1/3. Meter for your subject and shoot. You will be surprised at how good it looks. Not a lot of hard shadows and plenty of ambient light. I do it all the time and sometimes you can't even tell there was a flash.
Give it a try, it's film. It's a different medium than what the digi folks are shooting, so it takes a different approach.
Hope it helps,