Create a single mesh object. If there is multiple objects, Mesh > Combine.

Duplicate the object, move it to the side, Freeze Transformations/Delete History.

Select areas of the mesh and assign them different colours depending on each texture needed.

Go to Lighting/Shading > Transfer Maps…

Select the original Mesh as “Target Mesh” and the colour Mesh as “Source Mesh” (Add Selected) then select Diffuse. 

Select the output location and File Format to Targa.

In Maya Common Output, Transfer in UV Space and Bake and Close.

In Quixel/Photoshop, DDO, Select Mesh and ID Maps.

Select your materials for each section and click the little box by the layers to assign them to the correct area.

Select export to a file output location to use in Maya or Game Engine.