I've never had any "real" defensive firearms training and I've never had a firearms related dream but I did have regular, very realistic dreams about flight training when I was doing that, always the first night after training.
I also found that when I returned to practice the same skill the next day I was always better at it than I had been the day before.
It seems to me like your brain uses dreams to program procedural memory.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.