I got this gesture from the book Folk witchcraft so I thought id share.
When preforming, you will paint with your index figure to curse, or thumb to bless. You will chant a verse wishing your target what you want to bring them.. which you'll have to make up sorry LOL! Not dusting off my own for you but the book did give you a charm to inspire your own chant. I wouldn't use it to the dot, creativity keeps the spell harder to combat, so try and get colorful!
"Well may thee thrive, and well may the stead.
Blessed waters refresh thee and cup of life mayest thee drink thereof,
thy blood protected from shore to shore"
"Mote it be, I pray it"