Being I just blast it for metal purposes I dont have anything attached. Many though get fancy with it. Ive seen something as simple as a swaying hinged piece that attaches to the back so you can reduce the air flow. There are those that increase the air flow by adding extensions to the back for forced air inclusion.
This guy got a lil fancy with the back end piece twisting down and up for the vacuum air flow...
There is also another option of the "side arm" burner which uses the three way coupler. The air comes from the top. This though can be more difficult to acquire because most big retail hardware stores dont always stock that elbow reducer. I found one though at a tiny old town hardware store, those guys never disappoint.
Whats nice about that lay out is it lends the idea of using a MIG welding tip as your gas port instead of using a simple drilled hole. So between the gas port size, gas pressure, and air flow you can easily adjust your heat output. The metal forging community isnt too big when it comes to internet info but there is enough out there to give you the info you need.
Oh and use Black pipe not Galv. I see you had a Galv trash can. Eventually it will all burn off but still Zinc fumes are not fun things to inhale. Zinc will burn off galv stuff very easily its better to just avoid entirely. The main body of the side arm burner is galv but that part of the assembly doesnt get hot enough to matter, so really just focus on the areas that do.
Looking further at your vid Id say buy a pair of metal tongs. Or if you can weld make a quick set of them. Or drill holes and bolt a metal one. Very nice idea with the garden 3 prongs but the heat in a kiln could bring those dry wood handles on a warm day to the point of combustion and startle you. Im sure no harm could be caused since you got some nice gloves but it might cause you to drop a piece of work.
Looks good but I see youre using a weed burner as your burner. Sometimes these guys can get a lil choked up during use other than what theyre supposed to do. You might want to look into a Ron Reil Burner. Simple and easy to make and typically very cheap to make. If I remember correctly my first one I used a 1 1/2 reducer to 1 in pipe, a cross pipe of 1/2 pipe with a 1/16 gas hole positioned in the center. Its been a while since Ive made my last burner but with my furnace I can smelt copper so the heat output is there. The pic is it on low. Any higher and I would need a coupler on the end so the flame has something to hang on too. Easy and cheap and Im sure your top flue would be fine and you could even cover most of it to get the temp you need.
Ive ground down a stone before and it ended up in some pretty fine dust. I used a cheap tile cutter with a diamond blade and just ran the stone through it one line at a time. The catch underneath the tile cutter will trap most of the cut stone in a water slurry. Pour it off, dry it, and it crumbles to dust. I did this a year ago but never got around to testing it in a glaze. Im sure theres possibly a level of metal "contaminating" the dust just from wear and tear on the blade. Either way it beat pounding with a hammer and dealing with a container bouncing around as you hit it.
Oh and because you have to remove the guard on the blade you are bound to get a little wet so wear a face mask.