My boiler has bees going for about 5 weeks, and after seeing your post I decided to take a look. I had quite a buildup of flyash as well, not as bad as yours but close. So now I plan on getting out the vacuum every 4 weeks.
You are going to shut the boiler down every 4 weeks? It took me all evening to shut it down clean it up and restart. I can't see doing that all winter long.
Shut it down? No! This is my first year with coal and I'm determined to be a member of the one math club!
I shut off the service switch and let it cool for about 5 minutes. Opened the cleanout door and vacuumed the flue and the cleanout box itself. Closed the door and checked the fire ( if the fire was low I would have kicked it back on) Then I pulled out the baffles dropping and turning them a few times along the way, brushed and vacuumed out the tubes. Again checked fire, wiped down and reinstalled baffles then closed cleanout door. Now I pulled off the front cover, cleaned on top of the diverter baffle and the fire box. Put the front cover back on then took off and cleaned up the glass with a damp rag dipped in flyash. Start to finish all of 20 minutes.