Marcel, Adrian, Rob, Matthew, many thanks for the thums up!
Adrian,
yes, they are simply faint lines, I use acrylics, the key is thinning (depends on what colour you use and how visible you want the effect to be), colour can be anything that goes with the basecolours, as it shows through. I did it after shading, though I adjusted the shadows with a thin dark wash, and the midtones with an even thinner, so the original texture is left only on highlights, it also helps the shading of difficult camos - the light texture colour picks up the wash more, the base colours less, not alterning them much. With a thin repaint of the base colours you can tone down the texture if it went wrong.
Used light greenish grey on the Alpine (hence more visible in photo lighting), in grid pattern.
Straight lines of sunny skintone on the Jeff Shiu's at an angle trying to represent HTB material, but due to the scale went over the highlights with a lighter colour and did the deep shadow texture only with black, also, to control contrast, did the lightest pattern colour's texture separately, would have been too strong on the rest.
As a possibilty, the texture could be done before shading, then do the shading with lightened / darkened base colours, thinning adjusted to let the texture show trough.
There are many ways to textures, hope it helps and is understandable
Looking forward to see your version!
Denes