Thanks Fabrice.
I think you are right that the weathering of smaller scale models may look a bit extreme on the 1/6 scale. However, at the same time I want to portray my PIII as if it has actually seen action rather than fresh of the factory floor. However trying to give it a realistic "patina" without over doing it is the challenge. If there were more good color photographs of the tanks in action (rather than of museum tanks) it would be a lot easier to copy how they weather, wear and take battle damage especially DAK.
When I try to weather or wear certain parts I try to think of the story behind how it would wear and weather in real life.
I agree rust is often over done and not appropriate.
At the end of the day, as you and others have said, it is really a matter of personal taste.
In terms of the "Spanish School" of weathering I assume you a referring to the likes of Mig Jimenez, and I have to be honest, I kind of like the effects he achieve on the smaller scale models.
This is his 1/16 scale King Tiger
David