Just a thought, but it could be worth spending another couple of quid on an artist's brush set....
Dip one of the fine tipped brushes in the paint, and make a nice point on the end. Leave it to dry overnight, and you have the perfect point for dropping in the paint, and reaching the small chips to get finer detail, rather than some of the 'spray edged' brushes that come with touch-up paints.
The other option that can be used is cocktail sticks, but in my honest opinion I find I get better 'pen type' control with the brush.