Absolutely with out a doubt. "Any" practice is good practice.
I'd suggest an even split between offhand(no rest), and resting from possible "field" objects like trees, or fences. I try to take a rest when hunting as often as I can, but for some reason, the majority of my shots at game have to be taken with out the aid of a rest.
You might want to pay careful attention to how you actually use a rest. If you let your revolver directly contact a hard rest, it'll sometimes bounce off on recoil, and cause a miss, or worse yet, a wounding shot. Use the rest to steady your hands, wrists, or forearms, instead of the gun it's self.
The best practice I can think of (it's what I do a lot), is to hunt varmints with your pistol before deer season. I usually put in quite a few hours of groundhog hunting during the summer, which keeps me on my toes for deer when the season rolls around here in Virginia.