When we went we used the fat sharpie markers and the characters were appreciative. The CM's said they liked the fat ones because they are easier to hold with some of the costume hands.
Click-It Sharpie
I am NOT taking a Sharpie - I just can't imagine the hours of Laundry Stress! Especially staying at a hotel without all my laundry magic potions! (Alcohol will help remove sharpie for starters.)