You can buy long flexi drivers with 6, 7 and 8mm hex ends for hard to reach jubilee clips , but I like the drill idea, any excuse to use one
RE listening to the pump. All you need to do is turn the ignition on and off and it'll go into it's 10 minute after run program (regardless of coolant temp) and you should then hear the pump buzzing away without the fans intruding. It's quite a loud buzz, even on new ones.
You're right though, you won't notice when it's dead when driving, but the engine will take a lot longer to cool down when switched off on the after run program.