One route might be similar to the AWAC route where seamen man positions on a
couple of tours before reverting to their shipborne role.
There were three "exchange" slots allocated to dark blue on the Sentry mission crew back in the 90s. However, the RN decided to only take up one of them (the weapons controller slot). Apparantly, the RN wanted accelerated "promotion" straight into the Tactical Director seat (the chap in charge) rather than gain platform experience as a "worker" first, and so changed to an exchange with the Mission Support Wing briefing flight instead.