After the natural powder and two colours of colour powder, you dip one last time in clear powder — I swear this is less complicated than it sounds — and swab on some seal protect. Get to filing! It's easily the most arduous part of the process, because you don't want to file the precious powder off completely, but you also don't want to end up with bubble nails (yes, that was a thing). I got them down to a reasonable layer with a buffer block from Amazon ($7, originally $9).