Gradient effects that preserve original texture?

It's quite often much better to redo the entire sign rather than trying to mimic the original. This strategy allows for more options. Essentially, it's much easier for you to apply your own artistic interpretation of what the sign should look like instead of having to force your way through the entire process trying to mimic a natural, organic look which is of course immensely difficult.

I am currently working on a shot where I have to remove a tattoo from the neck of an actor and it involves motion stabilizing to simplify the roto, hand roto, several Photoshop files created from the timeline that I can use to remove the tattoo using a combination of the healing brush, clone stamp, color dodge, color burn, smudge, puppet pin animation on the PSD file to distort the image to match the changes to the shape of the neck, adjustment layers, animated gradients as lima track mattes for the repair layer to match the lighting changes, shadow masks, blend modes and a few things I have forgotten. One of the shots was just over 100 frames long and it took me 2 days and about 40 layers total in a half dozen pre-comps to effectively remove the tattoo. This kind of work can be easy, but it can be very difficult. You just have to break the problem down into the smallest pieces possible and not be afraid to combine layers to get the final solution. 

Without seeing the shot you are working on and/or your timeline showing the modified properties of the layers (uu) it is pretty difficult to give you any meaningful solutions. 

Here's a start on the next shot I'm working on that sounds something like what you are trying to do. 

By the time I'm done, I'll have at least 3 more nested comps and hundreds of keyframes in this 216 frame composition. I'm guessing it is going to take at least another 3 or 4 hours.

No such thing. The actual solution to the issue is to use blending modes like Color or Overlay to colorize your stuff instead of just plastering things over with Normal mode and then of course there is any number of techniques to extract textures from channels e.g. based on luminance which then can be overlaid using Multiply blending modes, used as track mattes or fed into displacment maps. This can be done with Channel Combiner, Shift channels and other such effects. Of course it will also require tweaking and a lot of finetuning as well as a deeper understanding of all the other effects and processes involved. No quick solutions here.

Mylenium