I use the blue water-erase most often, unless it's something where I'm going to need to press it before I can remove the lines, or if it's a color where the blue doesn't show. Then I tend to default to old school tailor's chalk, the kind that comes as a solid square or triangle. Hard to get really fine lines with that stuff, though.
I haven't tried the crayola washable markers - I should give those a shot. I've tried a lot of other things I didn't like for one reason or another, but I haven't tried those yet.