You've got the right idea in trying to soften the light, but often you need to make it less directional, and/or try to enlarge the apparent light source, as well.
"Enlarging" the light source, relative to the subject, will also help soften the light, and usually that is the game plan.
Why not try putting the light behind something like a white sheet, or else getting a piece of white foam core bord, and pointing the flash at that, using the FCB asd a reflector.
There are literally lots of ways to deal with harsh flash (and we need to remember that sometimes the harshness is exactly what we're trying to achieve) and while many of the solutions are very specialised (and expensive) there's lots of ways to make the process less expensive.
