I have used the remains from my smoker for meat smoking over the years. I have a large 5gal metal can with a removable top. I fill the can with wood chunks and put the lid on it and put on my propane turkey cooker. The lid has a 2 inch hole in it. I place the can under the meat to be smoked and lite up the burner. The smoke rises from the can onto the meat. This is a cold smoke, not a cooking smoke. the wood chips will smoke but not burn. When I am done smoking, I pour water down in the can top hole to put out any smoldering wood chips. This is charcoal that has been burnt with no oxygen.. After the char is cooled down, it has little to none nutrient value and is very porous. Putting the material as is in your garden will absorb any available nutrients and lock it up making it unavailable to your plants. The best way to inoculate the char is to go out into the woods and dig up some tops soil and blend it with the char. The char will pull out any nutrients as well as beneficial microbes and inoculate your garden soil. It takes about a couple days to fully inoculate your char, two weeks if you are looking for beneficial fungi. A lot of folks will soak the char in compost teas but poorly made compost tea will also inoculate the char with harmful microbes. I dont have anyway to tell what microbes my char is soaking up so I just stick with forest floor topsoil. I know a lot of folks like to make large amounts of biochar at a time and they make large barrels inside of barrels to cook their char. For container gardens, it doesnt take a lot and once it has been applied, you dont have to reapply every year. Another way to get char is to pull it out of your wood stove, just pull out some of the big coals and drop in a bucket of water, or sift your ashes and save the little bits of charcoal, it isnt the same as biochar because it is burnt in a oxygen type atmosphere, but its almost as good. I dont know what Hugelkultur is, I will have to read up on it.