First of all, thank you for taking the time to share so much of your experience with those of us who are new to the game. Without this forum, I may have given up on coal. But by reading, watching videos, and breaking wood burner habits, I have successfully made the switch! Again, Thank you.
One of my frequent comments when discussing coal (and Vigilant) tasks is that "I'm still learning." It looks like you are too, even after years of burning. That's great; I enjoy the learning curve, and relish the challenge of running the stove as well as I can.
I'm particularly interested in your switch from round stock poking to flat stock (slicer) poking. I found that with a pointy end round poker I could go down and back through the grill, and lift the coal bed gently to allow the shaker to do its job better, just as you described. But for clearing the space between the grills, I actually made a right angle hand tool to push the ash and coal back from the grill a bit. I use that if the poker doesn't get enough to drop away from the grill and through the shaker. I'll try the slicer again, but my awkward attempts early on are what motivated me to go to the rod.
I'm also fascinated with your flapper management. The pattern that I have adopted is as follow:
1) When ready for tending I open the flap to enhance the fire with the idea that it will help the new coal catch faster if I start with a hotter bed.
2) I then close the flapper completely in order to minimize air flow through the stove and do my first round of shaking, with the idea that the fly ash is better in the stove body than up the flue. If open, I noticed quite a cloud in the stove when shaking the grates.
3) After letting the ash settle for a minute I open the flap and the damper and commence the poking. I, like you, go along the sides and "lever" toward the center to upset the ash. I then go through about every second or third shaker slot and gently lift the bed.
4) I close the air down again (damper and flap), shake again (second time), and again let the fly ash settle for a minute.
5) Open the damper, flap and doors, check the ash pan and level the ash and coals, then close the doors.
6) I load 5-10# through the top; wait for blue ladies, then load the back center until the coal is about to spill over the grill.
7) When rich with blue flames I slowly close the damper, flap still wide open.
8) As stove top temp recovers I gradually move the thermostat lever to the position that I have learned will produce griddle temps in the 4-500 range, then leave it for 12 hours.
I'm quite confident that it would burn for 18 hours, but a thick fire, as you call it, is so much easier to replenish.
As you can see, my procedure is only slightly different from others, and everything that I have learned I learned from you, your videos, and others on this excellent site. I'm not kidding...three and a half months ago I knew nothing, except that I wanted to burn coal! I bought the Multi-Fuel version because I thought I'd have a wood stove if I failed at coal burning! I am thrilled to have gotten to where I am, and I encourage other newbies to stick with it. The rewards are plentiful. BTW, I burn nut, and am off to get another ten 50# bags tomorrow. Next season...a pallet or two.