How to make a gradient fill grooves?

Here's a quick sample, created as I outlined in my above post.

You can fill a layer with 50% gray and use the halftone pattern filter set to line.  If it's not blurred enough with the standard settings, you can then use gaussian blur.  You can then take that, adjust the input and output levels and create a 3D depthmap to plane, which will create the 3D image.

What Fill?

I don’t uinderstand what you are after – could you post screenshots of what you start with and what the result should be?