I just got a base trade, but it was a bit of work.
1. looked at the PBS bid awards, got names.
2. write up a short statement of what you want to trade,
3. went to mail room and put notes in the files of fleet/seat asking if interested
4. cross your fingers

I couldn't think of another way to get the exposure. The official way to do it would be post a note on the ALPA board asking about interest, but I don't think many people actually frequent the ALPA boards anymore.