Make a stop cut in front of the ears to extend the beard line up to the bottom of the hat.
Remove a sliver of wood in front of the ear up to the stop cut.
Make stop cut at the pocket line, and remove a sliver of wood down to this stop cut.
Make a stop cut to define the top of the mustache, and remove a sliver of wood down to this stop cut. (NOTE: This stop cut can be a rather tight arc/curve, and may test your knife's tip. The Murray/Mertz detail knife is up to this task, I'm happy to report.)
Make a stop cut to define the bottom of the mustache. Use the knife to remove slivers of wood up to this stop cut.