I did not train as a sub to become a Domme, but it was the end result of training as a submissive that I realized my place was on top, Dominance.
However, I do have friends who are Dominants and as part of their training did spend time participating in submissive activities. Switches??? No. Well trained Dominants? Yes.
I don't believe that training as a submissive or a submissive wielding a flogger is going to allow anyone the opportunity to get into or understand the headspace of their alter role, in a manner of speaking. A Dominant may learn how to use a horse hair flogger and feel the different sensations that vary with the type of swing or flick of a wrist. If He or She is truly Dominant, they will not necessarily understand subspace or the emotional and psychological components of submission. It is as foreign to them as being caught in a mousetrap is to an elephant.
Other means of training Dominants in the more formal end of BDSM culture include having a new Dominant mentored by an experienced and knowledgable submissive. I find this an interesting tact to take in training of Dominants and thought it may stir up the discussion a bit. Any thoughts?