You can also put out or snuff out a candle (I wouldn't be surprised if 'snuff out' was BrE only). The word 'snuff' is more common now in the context of videos that show a person being killed: 'snuff videos' [an odious usage, but it exists].
:-? Doubtful, I'd say. 'Douse' is not a common word (in any context), but this COCA link doesn't list 'candle' among the (fairly sparse) collocates. BNC (a much smaller corpus) lists even fewer.
That said, it'd be understood. I think it'd be more likely in cases of emergency or precaution, rather than just everyday snuffing;-)
If you have a question about the English language and would like to ask one of our many English teachers and language experts, please click the button below to let us know: