Just practice, screaming tutorials never helped me. Scream in the car or something or just get together with the band and scream your guts out and see what they think. A lot of vocalists scream/growl in different ways and there's no right way to do it (but there is a wrong way). Just push the air from your stomach, this is what people mean by not screaming from the throat. You're still going to do a lot of the distortion in your chest/throat area but these areas should not be taking the force of the actual scream if you know what I mean.
If you practice a lot and continously lose your voice, try a new technique, there's going to be some pain at first so don't overdo it when you're starting. The best setting to do all of this is definately a band setting as I've found musicians progress in skill far quicker when in a band.
