I've never tried matching fuel flow, because it just doesn't seem that important. It's never that different in the aircraft I've flown anyway. I match torques in the winter, because that's the first limit I'll hit. In the summer, I match N1's, because that will be the first limit when it's hot. Most of the pilots I know tend to either match torques, or sometimes N1. I've never heard of anyone trying to match fuel flow.