About the whitewashed T-34 issue - here's a picture of one in early spring 1942 - although it looks like there might still be snow on the ground, it's from March at the earliest:
Another photo, a rare one showing T-34's prepared to fire as anti-aircraft weapons. This photo is from earlier in 1943 again, as is obvious by how the crew is dressed, so the paint could have worn off in 2 months...
Finally, I think your best chance for finding a whitewashed T-34 at Kursk is here:
http://powstanie-warszawskie-1944.ac.pl/aa1/t34_kursk.jpg
Be warned this is a somewhat graphic picture. The dead Russian (wearing wrapped leggings, so not German) looks like he's been burned. I've seen the white on the tank been explained as some sort of soot related to the fire that burned the soldier, but it has drips and chips in it. It's most definitely paint. The tank has some charring on the front, but no real damage. The soldier's not dressed in winter gear, and there's no snow around the tank (the white stuff in front of it is probably some sort of soot, because it's too fluffy to be snow) it looks like the tank has had straw thrown on it for camouflage, which wouldn't seem very approprite if it was wintertime. Best of all, this photo is reportedly taken by a German photographer the week the Kursk offensive started. I've heard this photo credited such by two different websites, so it could be so. I don't know what the white ares in the background are - they could be water, but I don't think they're snow.
Anyway - do what you want with it - I think you could model a Kursk T-34 with vestiges of whitewash and be accurate (or at least not decisively wrong!)