Multiple materials on an object with texture from photogrammetry

Hi, I wondered if anyone had a (simple!) workflow for the following:

I create 3D models from photogrammetry and sometimes structured light scanning (or a combination of the two). So each model has a single texture, but often it has various materials, some shinier than others. For example a wooden statue with some gilding or a stone object with gems etc.

In Sketchfab I would like to be able to set different properties (specularity, rough/gloss) etc. on different areas of the model. Is there any simple way of doing this? Like painting a model in two colours and exporting it as a separate texture and assigning different properties to each colour (while still showing the original texture)?