I have D.tokaiensis growing in a fairly small brandy snifter (no option of bottom watering,so it's a pretty good example)
I just pour water in there every few days, sometimes I accidentally submerge them a bit, even, and they show no ill effects- from my experience the "dew" doesn't really dissolve in water, as long as you apply it gently
And what Jimscott said is true- with Drosera, super-high humidity seems to cause more problems than it solves, open tray is quite good enough for everything I have so far, can't stress enough that light is the key to dewey dews