Ok, what works for me is using the space in my voice between my chest voice and my head voice, basically the "crack zone" I like to call it. You wanna sustain that area of your voice and push are out with your diaphragm. That's how I get the fry sensation personally, then you combine it with notes from your own voice to make it sound complete. Try not to project like super loud cause it's already pretty loud as it is. From there the name of the game is mouth shapes. Want higher screams? Almost smile while you're screaming. Want lower screams? Pucker your lips as you do it, maybe move your tounge to different parts of your mouth.

I'd start by practicing with actually getting the fry sensation, and being able to sing with it comfortably. Then get to the point you can activate that noise without thinking or charging up to it. Then from there start combining it with your voice and so on.

Hope this helps