What to do when moisture forms on the helicopter's canopy in a weather front?
That won't happen "flying through a front" where the temperature of the plexiglass is at at or warmer than the ambient air - you just get drops forming and streaming back.  What has happened to me though, is condensation when climbing into a warm humid inversion on a sunrise clear sky departure where the surface temperature was much cooler than in the inversion.  On my airplane which has a sliding bubble canopy, the outside of the canopy fogged up suddenly at about 200 ft agl as the cool plexiglass hit warmer humid air and it was like the canopy was covered in wax paper.  A bit alarming initially.  I just used the attitude indicator to stay right side up, helped by the opaque blue of the sky above, until it started to stream and clear up on its own after a minute or so.