Technically you can't get one at the BWI--you'd have to go to the Villa's side. It not a spa, just a room off the workout room near the locker rooms.
I'm not sure there are facilities at the CR--I've never heard of anyone getting a massage there.
Not to worry, a mere monorail ride from the CR is the GF Spa. I've had at least a half dozen massages there over the years, all have been very good to fabulous. As an added perk if you go there for a spa treatment you are entitled to use the excercise facilities and whirlpool/steamroom complimentary on the day of treatment.
Anne