The beta isn't much different from the "normal" way. Just bring your best heel-hooking shoes and body tension
No Climbing Today!
^
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.