Ok Timelord, I'll try to answer but I don't claim to be an expert!
You are right that an AET is first and foremost a technician - he/she is not classed as aircrew. They would be one of the team of 7 maintainers on a typical Small Ship's Flight who has done the "winchman's course". As far as I remember, the course is only a week long and includes dry winching and wet winching serials. Once qualified, the Flight training directive probably requires them to do one day serial and one night serial per month - and that's about it! So, not a huge amount of training but sufficient to carry out occasional winch transfers/rescues in extremis (remembering that SAR is not the primary role of a Wildcat).
Hope that helps.