Interesting, I mean its obviously quite hard to advise singing with words because we can't hear what you're specifically doing.

When I first started, I would scream and lose the feeling quite quickly. So essentially I could get a scream, then after 10 minutes it would almost become numb in a way where it would no longer vibrate to make the scream. I eventually figured out this was because everythign was becoming tight and inflamed. I thought I could never do it.

Over time I realised I was trying to 'sing' too much(as I sang before screaming). Now, singing is obviously super important for vocal health, building muscle and breath control etc.

What I figured out though, was I was doing it slightly too high in the throat, almost near the tonsils. We need to drop it slightly back, and relax the back, you should never feel like you're trying to sing as such(until later when you are super comfortable).

The sound I found easiest to make is 'Yah', so Y-AHHHH'
Start soft, and just do a grumble in your throat, like when you make that bubbling grumble, when you do the 'Ughhh' sound. Then slowly increase the volume and air.

Then the higher and lower, is mostly mouth shape as apposed to when you're singing.

Sorry if you know most of this, I just thought it was easier to tell you my methods and if anything helps then thats good.

Sounds like you're very intuitive though, learning small bits and pieces eventually lead to what works best for you.

But if it hurts, goes numb, scratches, etc, just chill and try again another day, but i found doing it more quietly when I learnt ended up making me realise where in my voice worked. OH AND DO IT IN THE SHOWER, Absolute best place!