There is a vid on YouTube of that lad in Cheltenham doing it (Wellfair)?
I have done it but not with Weber. Although Weber ocr shouldn’t be a problem.
I serrate edge to flat, spat smooth, 2-3mm proud.
Then as it has got stiffened up so not too slump when you touch it, I ibar to flat.
Dont wait like you would with mono before ibarring, it needs to be wetter. As soon as you open it up the air starts to dry it. Have someone going over it with a plastic float as soon as you can or you will struggle.