You need both under and over fire air for Bituminous coal.
What type of coal you have will greatly effect your experience, what kind do you have, or where did it come from?
Bigger pieces of coal are better generally.
When bituminous coal first gets heated it produces a white vapor, that will burn if you have enough heat, air, and combustion source, if you don't this vapor goes up the stack and stinks your neighborhood up. Best results will be obtained by loading your stove so that flame is always visible above your coal bed, this helps with the heat and ignition source for those initial volatile vapors, once they start burning, over fire air supports this combustion and creates a cleaner burn.
This white smoke I speak of is explosive in the right conditions so don't just load a hot coal bed with lots of fresh coal and shut down the air, see puff backs, many threads on the subject. I didn't understand this and burned my eyebrows, and lit several towels on fire while tending the boiler in the shower house at my dad's mining camp.
I have Sub-bituminous C coal from Healy Alaska, your experience could become different, but I doubt it.