Lately, I have been using a new technique to apply pencil eyeliner:
I take a small, angled brush that I would normally use for a cream or gel liner,
I swipe the bristles against the pencil to pick up the color,
Then, I brush the pencil against my lid. I find that when I use a brush to apply pencil liner, I have more control of how the liner is applied. If I pick up more color on the bristles, I can get more opaque, rich color. If I pick up less color, I can get a softer, more subtle look. The pigmentation from pencil liner is also a lot more forgiving. With gel or cream liners, every little mistake can be seen. With the pencil pigment, you can cover up or fix mistakes easily.
The above pic shows a swatch of the MAC Blacktrack Fluidliner gel liner applied using a MAC 208 brush on top. The bottom swatch is of the MAC Feliner Kohl Power pencil applied with the same brush. Of course, the intensity and crispness is less defined with the pencil, but the imperfections are less noticeable.
I personally like this technique because I have more control over the liner application. Of course, most people like pencils because they are quick and easy, and using a brush defeats that. I do however think this technique is worth a try because of how much control you have over the liner application. Also, pencils don't dry out like gel/cream liners so if you don't wear liner often, you don't have to worry about wastage. If you are trying to learn how to use a brush to apply a gel/cream liner, this is a great way to get used to the brush application, before moving on to the gel/cream liner.
Have you tried using a brush to apply pencil liner? What's your take on it?