The footjam at the start makes the move possible. First it feels unpossible but at the last mm before reaching the hold, the jam lifts you up! Second trick: find the kneebar :D
Rain sucks, but broken holds suck even more. Remember, never climb on wet rock in Fontainebleau.
The sandstone becomes brittle, and pulling on it will ruin classic problems. Drying it doesn't help, because it's still wet and weak inside.
All you can do is wait for better conditions.