Andrea (and its sister Vallejo) are considered by many to be the best acrylic paints.
It's better to learn to highlight on figures tahn drybrush. Go to, picking the English language option, http://www.acrylicosvallejo.com and choose model color from the drop down menu. Scroll to the bottom of the page and there's an excellent, downlodable tutorial on using this type of paint.
That said, there are times you may still need to drybrush. Lighten your basic shade of paint and don't thin it. It's best not to use white for most lightening tasks. Rather, find a complementary color to do this. Now take a soft wide brush and dab the end in the paint. Wipe the brush gently on a cloth or paper towel until almost no paint shows. Drag this lightly across the details. Repeat with a more lightened shade of the base color paint. When it looks like you need one more swipe of paint, stop: you probably have enough.