I have answered you PM for the avionics, take a look at the video I linked as well
Basically, it seems the avionics will turn on automatically as soon as your APU GEN is set to ON.
Concerning the rain effect, I don't know if it's possible to use the default one at all. I'm not a modeller so I don't know the techniques very well, but what I've seen in the past consisted in two solutions:
- the windows were in fact panels, on which you can display gauges. Here, instead of displaying a classic gauge with numbers and needles etc... you just display a picture showing some water drops, or anything that blocks the vision of the pilot. Then, when the wipers are turned ON, the texture gets replaced by another one, similar but with a clean part where the wipers pass.
- a 3D flat object was standing in front of the window. This object showed the same texture as above... basically it's the same technique, excepted that you display the "wet window gauge" on this object instead of showing it directly on the window...