I did a stint with the stab jabs and thoroughly enjoyed it. Remember, polo's should be adminstered for minor injuries and extra strong mints for things more serious, such as a burst arm!!
There was plenty of serving folk doing it at the time ranging from chefs, rozzers, aircrew, techies and medics so it's definitely possible.
I think they are glad of the help anyone can offer and at the lower levels of the operation, they value the dedication and mindset of service folk, but beware of the crusty old feckers who pervade the organisation and believe it exists solely for themselves. They don't like fresh blood and fresh thinking and can make volunteering a frustating experience.
Im pretty sure there is an RAF Branch of the SJA but don't quote me on that. There might be something on the SJA website if you take a look. ( I haven't been on there for some years so might take a swift look again)
Good luck!!