Being on my third operator while flying the A320, there hasn't been a restriction or prohibition in the different OMs to refuel the aircraft. In fact, there have been provisos allowing the pilots to refuel if having to divert to an alternate without any company support. The reason I mention the A320 is because there is a "Refueling" supplementary procedure in the FCOM, and well... we do all the other supplementary procedures in there when needed. I even took my iPad last time I did it (I've only done it a couple of times, and SUP procedures are meant to be done in a "read and do" fashion, according to the FCTM
). Also, at one particular operator, I recall having CBT lessons about the refuel panel and its operation. This same operator also instructed us how to refuel the Dash 8.
Regarding the time taken to do it: since this wasn't an assigned routine responsibility, well... the couple of times I've had to do it we did depart late, and it was quickly reported that the reason we were late was because there wasn't anyone to refuel us so we had to do it ourselves. And we can only do so many things at once! Never heard back from those situations...