Not Shaun, but I might be able to help a little. I've found that it helps to keep the surface of either the celluclay or the tracks (or both) damp to prevent tracks sticking. I've seen some people put down plastic wrap, but I'd imagine that stuff would stick quite a bit. Even if the celluclay does stick, it's not a disaster since tanks don't leave perfectly neat tracks in real life. In fact Shep Paine in his "How To Build Dioramas" suggests using a screwdriver to rough up tracks left in celluclay for greater realism.
Just my two cents on the matter. Hope I helped a little.

How go you "spread the wash around"? doesn't it absorb into the groundwork?

Shaun, some really great info in this thread. Was hoping you could include the items you would change and let us know why. I think this will help us beginners to build more complete and well thought out dios. Pat

Sign suggestion: Design signs with place names (towns, distance markers, traffic direction, pubs, bars, gasthausen, stores, etc) on your computer and print them on decal paper. Looks more professional and is easier than painting them yourself. Works with any type diorama and you are limited only by your imagination.

I like the stained glass idea. It's one that never occured to me!

Awesome diorama! Got nothing else to add.

(Little advice: In German there is no "th" after the numbers. Next time just ask for translations for what you want to write in German. There are lots of German speaking people here and for the bean counters amongst us it's kinda funny when people make spelling mistakes .)

Cheers!