Well, you could always try to really study what glossed lips look like.  If you've got a few bucks to spare, Max Factor makes some really neat lipstick/gloss combos that have really good gloss effects.  I had a coupon, bought a tube for about $6.  They really show the detail on the lips, with the glossing on top. 

Or, you could get some photo references to study ;) 

As for which brush, that's definitely up to you.  I know that I use different brushes for different things than other people use them for ;)

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Knowledge is knowing a tomato is a fruit. Wisdom is not putting it into a fruit salad.