If you have a 3D rendering program outside of PhotoShop, another alternative is to see if that program has texture baking. So you'd import your model into that, do a procedural texture that's close to what you want, then export/save the baked on texture. In some cases the baking can generate multiple channels at once, instead of having to figure each one out on its own.

Sometimes that baking feature is neat to use to make patterns on their own for non-3D apps. Just have a simple UV mapped plane...

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.