i'm not currently "on the ground" but used to live there and still travel there frequently. Moscow has HORRIBLE traffic jam problems, so a lot of the answer to your question depends on when your people are travelling. If you're arriving at 5/6am on some morning (taking one of the midnight flights), you can make it to sheremetevo to olympiisky in 45 minutes tops. If you're coming in on a weekday during business hours, it could take 3 hours ...

Back in 1999, I used to leave the office in central moscow at 5:45 for a 7:30 flight from Shery. Then it became 5:00, then 4:30; now 4:00 or even 3:30 to be safe. Traffic in moscow sucks. (note that technically rush hour is 7am to 11am and 4.30pm to 8pm, but in reality it's bad basically from 5 or 6am until around 10pm)

Also, for the flight in, be aware that unless you're paying extra for VIP service, the passport line wait at Shery can be quite long - plan on an hour (though you may get lucky and get through faster).

Domodedovo is a more modern, and nicer, airport, but it's to the south of town, and Olympiiski is to the north - so it'll take quite a bit longer to get in. I haven't flown into Domodedovo for many years, so don't have hard info, but I understand there is now a train, which could be quite a bit faster. In the old days coming in to the center from Domodedovo was an hour on a good day, so I'd expect you're probably talking at least double or triple that now (unless, again, your people are arriving at 5am or something).

Good luck, and hopefully someone will answer who has more "hard" data than I!