Hey ur goal sounds nice.
However it might help if u'd provide us some further details about the real shot regarding light setup.
I'd imagine that scene in more real lighting revealing for your actor
[let's say a silhouette back lit of him ]
so this light making a contour first as the cg-footage rain blends in,
and later on reveals all of his features.
I hope u have your shot with some real water raining on him as well.
I'd recommend you to check for a real rain footage to boost your realistic fx.
Maybe you should use you rain layer as a track matte Lumma/alpha
for your talent.
or even some cg follow focus that travels across your rain layers to the one of your talent.
I guess that since u'v done with ur shooting now only cg+compositing left to run.
So u wanna make a realistic one or something like sin city?
I was planning on shooting myself as the actor against a wall then using a rotoscope technique to remove myself from the background.
Then I presume I could play around with the CC Rain and use it to unmask myself, I just want it to look as if I appear out of the rain standing with my back facing the camera. Like a mysterious looking sillouette. standing in an urban environment.