I don't have the slightest problems with wet races, as a matter of fact, I find them even easier than the dry ones. This is simply due to the fact that you can comfortably overtake everyone on the first lap and then just sight tight in P1 until the finishing line without having to pit. If I recall it correctly, I won all the wet races in my first season with Williams on Expert without abuse of the 11/11 bug or any other shenanigans.
Here are some pointers:
Set up: Extremely high front and rear wing for maximum downforce; low gears (accommodating for both the fact that you're running with more wing and that you can't go as fast in rain in the first place) and medium-low brake pressure (better go low if you're not a pro in the wet, especially with heavy rain)
Driving style: Be smooth. Very smooth. No sudden movements, that goes for the steering wheel as well as both pedals. In the rain, it's most important not to do anything hectic, because if you do, you WILL spin. I feel that this is considerably more difficult than in F1 2010.
Practice and Quali: There's a bug here, if you fast forward while in the pits. The AI times are too fast because the game thinks that the track is already drying, when actually it isn't. So, never stay in the pits in Practice and Quali. I know this sucks, but it's the only way to actually make the track dry up. If it stops raining and you sit in the pits for another hour, the track will still be wet once you come out, but the AI will have set times as if it had gotten dry through usage. So just park your car somewhere, do something else, and come back once the track is dry.
If there actually is heavy rain throughout the entire quali session, you might as well set your lap right away, just don't pit, because then it will bug out again and the AI sets fast times on a whim. However, that being said, the AI is pretty good in heavy rain Quali sessions, for example I only managed P3 in Singapore (where the AI really sucks in the dry).
Hope this helps :wink: