Unfortunately all the allowed materials are already noted, and a whiteboard isn't one of them. You'll only be allowed 5 blank pieces of paper to write on.
I have yes. I think when it comes time for the PT, I blank and everything I learned, especially with LR seems to go out the window. I definitely have to get my timing down more as well. I feel like I rush and that doesn't help in the slightest.
From what I've read, you're allowed to have a bottle and 5 pieces of scrap paper - you'll have to show both sides to prove that they're blank. There's a lot of info on the LSAC website about the requirements.