A short & sweet video on diorama grass: http://www.youtube.com/watch?v=_kpMBL76_VE
Insofar as tracks are concerned, rule one is: find a photo! (I'm currently working on the Pegasus War of the Worlds diorama, and being a fussbutt, I need to "ease" the pre-cast tread marks because if you check the actual footage, while there were clouds of dust, the hardpan didn't take track marks for crap! On the other hand, I've got this GREAT photo of a tank CLAWING up a steep slope, and I've already stashed the IS-3 for when I get around to it.)
I've used two techniques for making tread prints. I've pressed greased caterpillar treads into "mud", let set, and pulled them out. I didn't care for this as (1) I messed up keeping the tracks parallel and (2) it looked too stiff, more like railroad tracks than tank tracks.
Second technique (full disclosure: I haven't used this with a tank... yet) is to make an axle and mount an appropriately spaced pair of wheels with some kind of a handle. I trimmed down an old rubber stamp, used it as both axle and handle, and rolled it around a bit. It made decent jeep tracks. When I get to that IS-3, the plan is to turn wooden wheels that approximate tread width and spacing, and then to roughen them on my bandsaw to match the tank tracks.
Occasional factual, grammatical, or spelling variations are inherent to this thesis and should not be considered as defects, as they enhance the individuality and character of this document.