I used to bite my nails and it took a long time to stop. I actually stopped based on a bet my sohpohmore year of high school.
And the way I was able to make it through the bet was by having a best friend, Amber, who lived across the street. How did that help? We painted nails after school all the time. As soon as they looked a little shabby we would redo them.
So I have had lots of practice doing my own nails. My tip to you… rotate your finger and hold the brush steady. That has always given me the most french tip success.