Weathering and trick technique, do they work?

Before (black oil wash with sediment on base colors):

After:

Woo, it worked! Ahem. I was buying pens the other day and saw there were oil-based Sharpies. This reminded me of something I had heard about using markers to do the trim work on Chaos models (particularly Heldrakes). So I picked up a gold one because Death Guard love their brass and the actual brass marker was really dark.

I'll do a little highlighting/shading once I put down matte varnish, but this needs a few days (at least?) to really dry.