As AA62 says, AT crewing was similar to that of the airlines, albeit without a specific crewing department organising it. Rather, it was co-ordinated by the aircrew leaders to ensure 'equal misery for all', or joy depending on one's viewpoint. Certainly any goodies such as sought after trainers (empty aircraft, other than a spares pack up, 'flying the flag') or detachments (like Supply Dropping in Borneo), were scrupulously shared out fairly and evenly. Training requirements of course had to be accommodated too.
The one exception in my experience to that pattern was on Hastings at 24 Squadron. The Boss crewed up his Squadron in much the same way that Bomber Command did in WWII (though then they chose one another at OTU, I believe). As a new captain I was lucky, and was allocated a superb crew. Others of course varied and the practice was not generally widespread. The main objection was the effect it might have on standardisation, which was essential if crews were made up ad hoc on a daily basis. If they flew together on a semi permanent basis then nods and winks could begin to unravel the SOPs.