I've never done anything but once upon a time, back when Smackjeeves was still alive and popular, there was a BL creator who drew mini promo comics for their webcomic to hand out at cons. I'm not sure how successful they were, the creator was a little... intense?, but it's a pretty neat idea if you have the money for printing. Nowadays you'd be able to add a free-generated QR code to make access to your webcomic and/or socials easier too.