I know this is a bit late, and unfortunately I have no recommendations if you are still looking, but my band is now in the same situation. We just lost one of the best unsigned screamers I've ever heard and now it's apparently up to me to get better. I can only add some distortion onto normal signing, or my screaming is that really low rumble and I have no range with it. I heard about those screaming DVDs you mentioned... are they worth it? Do they help? Any other advice?
Bassist and Vocalist... ughh