I'm not big on techniques, blah blah blah-- but there's some techniques that screen naturally and avoid any traces of Mr. Funny Man.
This is one.
This is best for nightclubs.
If you see hot girl, lock eyes with her, smile/smirk, then give her the middle finger.
If she's cool, she'll play along and probably give you the finger back (or she'll shake her head and smile).