Workflow from Revit or OBJ files

I am new to 3D and Twinmotion. So am looking for a little advice.

As source material for TW scenes, I get RVT or OBJ files. They open in TW but often want/ need adjustments that TW does not currently seem to do such as placing an exterior material on the outside of a wall and an interior surface on the inside - it seems you can only have one or the other. I have found workarounds but it is sub-optimal. Like making a copy roof and lowing it 2 cm to apply the interior ceiling material. Or making siding and roof panels in Sketchup and sheeting the TW house.

It might be nice to have a TW feature where there is an option to apply a material to a single face (?).

I am curious about what workflow others may have.

before ​export obj,give each face a different material,then replace at tw

Thank you, yes, I apply placeholder colours when creating my own assets in Sketchup.

My current obstacle is that I don't have Revit. So I would like to know if anyone who does not have Revit or SketchUp Pro has an effective workflow from receiving an RVT or OBJ file from a client that does not have the surfaces or object materials differentiated. Other than going back to the customer and asking them to colour everything for me :)

I haven't found a monetarily accessible (free) way to do this yet.