Interesting Jeromemsn, how we all evolve methods that work for us. Why would your Harman grates get stuck? Why can't you fill 90% of your coal bed all at once? If the Hitzer ashpan weren't as shallow as it is, I'd probably wait until the ashes cool, too, before emptying them. But with a big load of ash, the ash in the pan is very close to the underside of the grates, and I would be concerned that I wouldn't be getting enough fresh air to the grates, especially when I'm trying to get new coal lit.
I think one HUGE variable, in how each of us works with our stoves, is the amount of draft. Mine borders on being too much, but one advantage of this is the vacuum effect to suck fly ash up and out the chimney. I see this most clearly when I put the empty ashpan back into the stove. The movement of dropping the pan (even 1/2 inch) after I've inserted it all the way causes a little puff ash, but this is immediately sucked back into the stove. I have no need to use a vacuum cleaner, except the hearth getss small amount of ash and coal dust on it, which I wipe up with a damp paper towel.
The big draft also means that livening the fire, and igniting new coal, is a pretty quick process. I have also, a few times when I've forgotten that I left the ashpan door open, heard a bass note--like the bass note of a pipe organ, but a little less pure in tone--start to build in the house
I rushed in and half-expected to see the cats clawing the carpet to keep from being drawn up the chimney