Hi John, nice Sherman, but, I feel that the effect is not quite there yet..
you are trying to depict a worn winter camouflage. But your paint effect has very sharp edges. It doesn't look worn and dirty enough to me....yet.
Drybrush the edges of the white with white to make them realy blend and fade out.. And It looks like you (dry)brushed over the white, rather than use a wash.. if you use multiple washes, it gives that deeeep, dirty look of several weeks in the field. Remember, layers are the secret..
You did a good job with the periscope guards, are they scratched?
groeten
Henk