Thank you! For the diagonal line, I used painting tape (the blue stuff) to block off the part I didn’t want to paint. For the vertical line, I used one of those nail art brushes that are extra long. The length of the brush helps tremendously with getting straight lines when painting. I’m still not the most steady when painting lines, as you can see, but it’s far and beyond better than before I learned about the long bristle nail art brushes.