[Karen Hart]

This is a difficult situation. 

In order to grow breasts, you must have dominant female hormones but that entails at least some loss of erectile ability.
The best strategy that I can think of is to take just enough herbs to where you just start losing erectile ability and then back off if it becomes too much.
As your ability starts to come back, increase the herbs again and try to maintain that ebb & flow. That might be very difficult to maintain. 

Yes, these herbs can make you feel more feminine and, to more enthusiastically pursue femininity. I don't think that is a given but I know it is true for many people.
Also, more breast growth can drive you to crave even more. Again, not a given. It does not work the same way for everyone.

If you want to try PM only, go for it. Most of us, if not all of us, learned what works, from our own experimentation.

I hope some one else can chime in with better advice.

Karen