What to wear for Jay: Baggy pants; large black t-shirt, preferably with something offensive on it; yellow parka; and a black beanie. You also might need a long blond wig.
What to wear for Silent Bob: Sport some facial hair (if you can), put on a backward white hat, a black t-shirt, and a big coat.
How to act: If you're Jay, you're angry and loud. Swear a lot. Silent Bob is pretty self-explanatory.