Here is a little trick for doing Animated signs in Nuke for city matte paintings at night. It is very easy. You can bash out a bunch of different signs and get them animated in Nuke very quickly.
This is what your animated sign cards look like in Nuke after you are all done.
Here is a Video walking you through the process:
To make these animated signs you start out with a image of a sign (here I chose "Fry's Celebrated Chocolate" for obvious reasons). Make a selection and a mask of these letters and put each one on a different layer. Now in Photosop use the "Animation" tab to animate the letters turning on and off. To be honest I have not used this the animation tab very much in Photoshop but here it comes in really handy. Then under "Export" you can get all the frames out of Photoshop as an image sequence--make sure you are exporting them as pngs or tifs with the alpha.
In Nuke premult the image and then add a "retime". The retime will make the animation loop and control the speed of the letters turning on and off. You can make your 20 odd image sequence into a 100 frames of animation with this node. Then put a glow on it with or what ever effects you want. Then put it on a card and move it into place. That is really it. I have used this and it is a really easy way to get some life into matte paintings.