Here's my contribution:
https://z4-forum.com/forum/viewtopic.php?t=137897
The button units can be dismantled to allow the surround to be sprayed without having to mask off the individual buttons.
Someone (Inkey$ or Street, IIRC) did a thread the other week including details on how to dismantle things (4 torx screws from behind, 1 each side, 2 in the big piece.)