It can be ignited with a percussion cap if at least a 5 grain booster charge of conventional powder is loaded first. But I haven't heard much about how it performs in a C&B revolver when the booster charge is properly placed. And I haven't tried any of it myself.
Blackhorn 209 is an extremely fluffy powder. The cheapest way to get it is to call Ed's Gun Shop and ask for Carlos. Including delivery, his price may actually be less expensive than the average retail price, but the minimum order is 2 containers.
Some feedback by a poster who appears to have improperly placed too small of a booster charge directly under the nipple of his ROA when loaded with an unknown volume of BH 209:
Link to info. about using at least a 5 grain booster charge: