I've always used a manual wipe with kerosene using lots of clean rags and plenty of dry wiping. My manual recommends kerosene and cautions against using other solvents which might damage rubber o-rings. I do this every 600-1000 km depending on how I've been riding and through what. There are brushes available as well that grip/clean both sides of the chain. Haven't tried one, but suspect it may do a better job of penetrating all the bits around the o-rings and such. My manual specifically cautions against using a brush, again, for fear of damaging the o-rings. I visually inspect to make sure that each roller is undamaged and spins freely during the cleaning and subsequent lube job.
There are probably a lot of chain-cleaning techniques being used ... will be interesting to hear a few.
BTW, I've got 34K on the Bird's chain, and guess what I'm shopping for next ... new chain and sprockets (can't have one without the others) ... mine still looks pretty good with respect to the shape of the sprocket teeth, but she's stretched into the replacement zone on the indicators ... I'm still debating about changing the sprockets (number of teeth and maybe manufacturer) from stock ... it's nice to have the top end speed, but rare to get to enjoy it ...
Any experience/thoughts re aftermarket chain/sprockets?
cheers
p.s. not a good idea to use gas ...