I tried both a brush and my fingers to apply the glitter, and I found that using the brush made the glitter blend into the lip color a bit more. I opted for my fingers so I could truly show off the glitter. Also, the sparkles' jar is fairly leakproof (which is smart!), so to get a good amount of glitter out of the jar, I'd suggest tapping the bottom of it on a table a few times.
Image Source: POPSUGAR Photography