Lol, the rain isn't that difficult. I followed the rain tutorial Ninja gave you, to an extent. I just added a layer, made it black, put the Noise in, then used motion blur, repeated that a few times, then used Eraser to fine tune the edges of the Marines. Afterwards I used a small scale spray brush and outlined the marines to make a fake droplits effect. At first it seemed difficult to grasp, but it's actually quite elementary. I'm sure you'll do fine.