Big pens, sharpies work great!!! as long as what you want signed is not on your body, it is signable. Don't wear a shirt on and expect them to sign it, it has to be off of your body. Green sharpie is not supposed to be used but there are different ways CMs approach this......ranging from letting it go to being careful to asking politely if they can sign with other markers, face characters usually don't have trouble signing in green. A large vinylmation is the best to get, it will be hard for them to sign sometimes but they usually take the extra step to make it work. You may need to hold it for them while they sign. PLEASE resist the Kooky Klickers. They work fine for face characters, so let them be used for that and bring sharpies for fur. Trust me, they are horrid to sign with.
Have a Magical Day!!!
Goofster18