As far as how much shaking and how much ash should you get:
I am a "first year" coal burner. I have heard time and time again that "every stove is different...." In that respect, I was shaking until I see red coals, but I have found that is NOT enough. Over time, performance would begin to suffer and it would get worse and worse. I found that the ash would start to accumulate and choke the fire. I now (at least in my set-up, yours may be different) have the following mantra:
COAL INTO STOVE = ASH REMOVED FROM STOVE
Basically, it means that I now have a general idea how much ash is produced by a certain amount of coal....I make sure I remove "x amount" of ash when I had added "y amount" of coal, depending on how much coal has been burned. On nights where I have really loaded up the stove more than usual....the next day I make sure I get extra ash removed during shakedown.