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