It's the details that give real life and credibility to this sort of trompe carving.
A strong detail here is the array of seams that run from the button at the top of the cap to parts of the edge. Not all caps have this particular arrangement by any means but the principles of carving them will be the same: Think shallow relief.
You'll find a shortbent V tool useful for the deeper hollows but failing that I'll give you an alternative approach for running the seams in tricky areas.
Shortbent skew chisels (left and right) are also useful. We have a video about them here.