i do the wet towel over my screen top & i also have 2 water dishes, one of which is directly over the heat pad on the warm side
(speaking of which, why wasnt that mentioned when listing ways to increase/create humidity?)

now as far as the issues with digital hygrometers being erratically inaccurate & the mention of accu-rites...

i have an accu-rite and i must say that when my girl has gone into shed i've increased the humidity & even let it max out as high as the accurite can read it without there being condensation and my girl has yet to have a bad shed. when the accu-rite reads "HI" for humidity its s'pposed to be over 90% but even at that level theres never been condensation.
even if it were giving an inaccurate reading, obviously its high enough to prevent a bad shed.
i'm not saying your experience with these things is wrong...i'm just stating what i've observed.