I used to do this at times when I didn't have my own gel liner. It works wonderfully as a liquid liner and goes on smoothly. Basically, remove your mascara wand and dip you angled brush in the dollop of mascara that is on the tip of your wand. Use as you normally would with the angled brush.
This is much easier than carrying around an angled brush, mascara, and a circular bottle of gel liner or a thick liquid liner container. Plus, I'd probably be taking an angled brush on vacation anyways if I'm big with darkening my eyebrows.
Just a thought.
Hope this helped! :)