On my titan, I did the chipping very simply by adding a bright silver-gold (whatever your sub-extreme highlight is) dag, and filling it or off-setting it with a very dark brown.
Do the highlight first, you can then paint the dark colour over it to sharpen it, rather than attempting to paint stupidly thin lines under insane control. If possible, always find the lazy way.
I wouldn't suggest using sponge method, as you're likely to get it in the wrong places, which will then need fixing. A good pointy brush and some patience is the quicker method for this situation
IMO.