Sue, my char goes in the garden, and the big John Deere rototiller will smash it into powder over time. But in a raised bed or pot-based garden, the best results come from finely-ground char.
Like ashes, char will tend to raise the soil's pH. Sounds like you can add a lot without worrying. I have to watch it, my clay-based soil leans toward alkaline/basic.
My charcoal-making is incredibly primitive -- a Bic and a long-handled spade. When I have a fire in my big firepit or my Landwave mobile burner, I just keep tapping away at the partially burned material and packing down the charcoal to keep the air off it. I have done this for years for natural-wood barbecuing. When the pit is full, I spray it down a little with water (don't saturate) or add a little snow on top, and then put an airtight cover on it. The steam plus cover kills combustion. Done!
I'm planning a better system. I want to make use of the heat produced (I'm in a winter climate) and I want to cut down the amount of smoke I eat (*koff*).
I like this simple setup using two different size metal pails/barrels:
http://www.holon.se/folke/carbon/simplechar/simplechar.shtml#two barells
I'm really intrigued by this burner/charcoal maker:
http://www.treehugger.com/files/2010/03/biochar-breaks-through-in-haiti.phpThe other option is to use a "cartridge" system with my existing wood stove. Short pieces of stovepipe with metal caps should do it.
Long post, sorry 'bout that.
Doug
P.S., if you char grass instead of wood, you will get instant powder. No need to grind it.