A buddy of mine and I are flying PIT-IAD-LHR 9 MAR 16 (UA122) on K fares. Assuming I complete my booked travel before EOY and hit 1K, what's the process of buying up to W to apply GPUs? Right now it's showing R=0 so it might be moot but I'd like to be able to track just in case. Also, is it possible to buy up to W on just the int'l legs?

Thanks!