In reply to Ha77on:
some appear to have missed the point you want something to do while at work.....
Rather than technique, my own recommendation would be take guidebooks with you and make progressively harder lists for stuff to do that will motivate you and plan ticklists for a given day. You can easily sneak a guidebook into other stuff and hide it under stuff to give the impression of working. Paul Nunn's Peak District guide got me through some hellishly boring shifts.
(Many years ago while a student and doing shitty jobs I found there were few jobs you couldn't find some training or bouldering problems at. My favourite was a warehouse where I could layback up the metalwork the shutter ran along when the chain skipped off to save getting a ladder
)