i used a kneebar for the start and then stuck my foot into a hole. made the start pretty easy. when you‘re taller or have a stronger core you can do the „jump“ less dynamic and keep your feet where they are. would have worked for my height. but my core decided it‘s impossible :)
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.