Russian tortoises' shells usually do look a bit rough. May I ask how this tortoise is housed? And do you soak him or does he have water in his habitat?
It would not be harmful to occasionally apply cold pressed coconut oil, rub it in, allow 15 minutes for it to absorb, then polish it off with an absorbent cloth. Normally shells don't need topicals, but when they show dryness, like yours, a bit of outside help won't be harmful.