Personally we just beat the living p*ss out of it and drop an alchemists fire on it. 1d6 real damage/ round will kill it. Usually they don't get up, but if they do just knock them down again (they have at best 5 hps and are prone while burning).
Multiple alch fires do the trick if you can't stick around, as do a few acid arrows.
Otherwise a bonfire works (bonfires do more than a mere 1d3 a round- can't remember the exact damage).
You can't really CDG them in anyway, unless you've got a flameblade or something similar (which works better than anything). Flaming sphere planted on them works very well also.