My thought is always go to what you would do in reality. These sets were mostly applied in the field as kits to upgrade an existing Panze, probably during refit/servicing. They would have come from the manufacturers in Sand Gelb. They would then be attached to an existing already painted vehicle. I think, therefore that while the outsides would have been camouflaged to match the vehicle, no one would have wasted time camouflaging the inside of the schurzen. Also remember, that often schurzen would have been taken from knocked out tanks to make good damage on serviceable ones. So you can easily get different non matching patterns. Good books for ideas are the Panzer Colours and D-Day to Berlin, all by Arms and Armour Press. IIRC D-Day to Berlin is by Terrence Wise and Panzer Colours are by Bruce Culver.