I have tried 3 different brushes for gel liner application. Two of them are MAC Holiday SEs and the other I just thought I pick up to test was the Sonia Kashuk angle brush. The gel liner I use is the Bobbi Brown Long Wear Gel Liner.

With the smallest angel brush from MAC, the 208 Angle Brow Brush, it still creates a rather thick line and since the brush is on the hard side, to me it's not as flexible. I like to tightline the top, so a softer brush seem to work better for me. The Sonia Kashuk one was nice that it has an angle to the handle/metal part, but the tip although looks small isn't really that pointy. It tends to grab too much of the gel liner and can result in thicker blobs, just not a consistent application.

The other is a MAC 316SE brush (which is really a lip or eye brush) is my favorite for gel liner. It has a soft feel and the brush is flat and tapered but provides more flexibility. I also tend to like the softer and natural look. So I do want it as thin and light as possible. This MAC 316SE brush is also soft enough so if I accidently poke myself on my top waterline (yes it happens to me!), it doesn't hurt like the harder brushes.

I know there is a 316 covered brush and also a 318 retractable brush on the site and I think I might just have to get those also..ok, at least one of them!