For the online GMAT, I used:
-Acrylic whiteboard
-Bic Velleda Fine Whiteboard Dry Erasable Pens*2
-Whiteboard eraser
I love my acrylic board because it is hard and can be used in many angles without always having to be flat on the table. Plus it is perfectly white on both sides. Make sure to buy a round one as a square one can be quite sharp at its angles.
The bic Velleda pens are just perfect (except the black one which is harder to Erase). I really like the feel when writing and they are fine enough to write naturally and in quantity.
I selected an eraser with no marking and no branding on it.
Remember to show everything, both sides of the board, both sides of the eraser, your desk and surroundings, even your ears before the exam and at the end of the break. Both sides of the board before taking the break as well.
With all this, the exam goes well and validation goes smoothly.
Posted from my mobile device