This is the nail drill that I have. Its nothing to special but it definitely gets the job done. Plus its pink and blue
This is a diamond drill bit used for backfills. There are several different shapes you can use, but this one works easiest for me.
So here is my thumb nail after its drilled. You work the diamond bit from right to left until your smile line is etched and then remove the rest of the acrylic or gel from the free edge.
This is just a photo of the in between stage. Once I'm done drilling, I go back with a regular file and file the smile line so that it is even and crisp.
After all of that was done it was time to start adding in your color. I was using gels here, so I first put a thin layer of red gel paint in the area that was drilled out. I then sprinkled the red paint with red and orange glitter and cured it in a UV lamp for 3 minutes. Then I covered everything with a clear gel and cured again for 3 minutes. After that all you have to do is file into shape and apply the sealant (or topcoat). Here's a few pictures showing the end result.