repeating steps 1-4 would make a rain layer...so do that 5 times in order to make 5 rain layers (change the noise % and possibly the blur % for each one in order to make each rain layer different)
then go into image ready and make 5 frames, first grame has one showing, then second frame has a different one showing (each frame has a different rain layer showing) dont have more than one rain layer visible at one time