I just did this on an old marker board and it worked well! I covered the floor in front of the board in case I sprayed on the floor. Ended up, I used way too much spray. I really does take very little. Don't spray the whole board!
Clean the board the usual way, then spray on a little WD-40 and rub it in and off. I had to rub quite a bit because it was so slick. I'll know next time to use only a little.
I have not used WD-40 on my whiteboards but I have used it for other things. Be prepared! It has a very strong solvent type smell. My custodian used it to loosen up my window jambs for me when they were near impossible to open by myself but the scent was very strong and lasted a long time. Goo Gone has a scent that some people find objectionable but it also has a citrus scent added to it that helps a lot and I think is easier to take. Use just a little and keep the windows open if you are sensitive.