Thank's Banita! Helped alot.
I did this also back those days but couldn't remember clearly. There was also a reason I seperated the different things in parts (a collection of surfaces).
I think I've done this, cause it was easier to use similar textures with different objects, but as said before I have really no more clue of this.
I have to relearn the whole process, but the more I work on it, the more comes back to my mind again.