Animating background crowds?

Hi! I’m new to toonboom so was just curious if anyone has any advice. RN im doing a short animation, and its focused on the main characters, BUT i wanted to have some blank crowds in the back, to bring the setting to life, but other than drawing each character frame by frame i have no idea how to do it. They dont have to have details, honestly just some blacked out silhouettes would work. Anyone have any advice on how to do this quickly/not complicated?