I'm not sure I completely follow. You are making unique textures, and relying on the V-Ray render process to write those unique textures out to our texture cache folder. Then you're using photoshop to manipulate those textures in some sort of batch operation, correct?
From what I gather from your post, your goal is to grab all of the textures used in your current scene, and place them in a more user friendly location, is that correct? I would use the 2.0 "pack scene" feature to achieve this. The scene file, and all external file dependencies will be zipped up so that you can move the files anywhere you want. We search within 3 directory levels of wherever the scene file is, if we can not find the files on disk using the path that is specified for that texture, so as long as you keep the textures in the same directory, or within 3 sub directories of the scene file, the scene should render using the textures that were packed.
In V-Ray for SketchUp 2.0, you no longer need to (or can) have a shared folder that is used for DR. File transfer happens behind the scenes, and it's fast. The whole asset collection nonsense is behind us now.
Also in V-Ray for SketchUp 2.0, the cache folder should get cleared out. I can't recall off hand if it's every time you open/create a model, or if it's something that happens according to timestamp of the texture, but either way, it should be getting cleared out on occasion. If that doesn't happen, please report this bug.