My local airport desk agent has done this a couple of times for me. Once using 500's and once using miles. The first time they had to call and learn how - took about 15 minutes. Nothing had to be signed just ID and an entry into the record; second time was miles ug non-premier a signature was needed as well as ID. Card stated I agreed to the tranaction - DA told the receiving person was to keep the card with them.

No experience with HK-49. But I would try an airport DA instead of the wonderful IAD 1K room.