David Crocker's Solutions blog
Scroll down to Bed Surface and there it is in the last paragraph. But it is necessary to have a PEI Sheet without glue on it and a seperate adhesive sheet like the 3M 468MP. But as i already stated i´m not satisfied with the result yet. Maybe the coating didn´t "connect" to the PEI sufficiently... Might depend on the used spray. I can´t find the one i used but this one seems similar BBQ and Stove Paint
Perhaps try a longer or higher temperature in the oven. I don´t know how far you can go though.