I am a decent metal vocalist. I have taught all kinds of people to do deep guttural growls, from children to adults male and female.

Without creating a wall of text that will only confuse you… Two words: Exasperated sigh.

Sigh like you just died on the final boss and realized you never quicksaved.

Sigh like your dad just made the most anguishingly bad pun you’ve ever heard. There needs to be some disgust in this sigh.

Kind of say “uhhh” and “eww” and “ugh” at the same time.

The goal is to push air hard and leave the throat muscles loose. This will make your throat flap about and distort the sound coming out.

Okay we’re getting toward wall of text, but, have you ever had a cough for a long time? And your cough got nasty sounding, even after you were all better? You trained your muscles to relax, thats why it sounds different, and you did it to help push mucous out. Screaming is pretty much the same. Once you’re comfortable with all this, give it a nice loud: “Ahhhhhhhhhh!” But relax your throat as you push more air/push harder. That’s where the distortion comes from.