dry brushing is real easy, once you get the hang of it. simply put a bit of paint on your brush (as you normally would to paint) and then on a clean surface (such as a piece of paper) brush to get rid of the paint you just put on. little or no paint should come off before you are ready to 'dry brush'. on your model, brush over the desired surface and the end result will be that the raised surfaces will be highlighted. this seemed strange the first time i was shown how to dry brush, get rid of the paint before you actually pain?? trust me it works a treat.
i suggest you give the technique a bit of pracice on something other than your new fang dang model to get the hang of how much paint you need on the brush etc.
the advantage of dry brushing is that it will only apply a little bit of paint at a time so it means that there is a little bit of room to make a few mistakes.
remember the best way to learn is give something a go and then practice.