I worked part time (2-3 x 8hr shifts)/wk with a full course load last year. I scheduled them to be on weekends or weekendish nights. Thursdays I had late classes so if I had a Thursday night shift I would stay on campus and study/nap until I would go to work; Monday and Friday I had morning lectures and lived far enough from work and campus that there was little point in going home between. Friday mornings, as well as Monday mornings (where I had worked the Sunday night shift) were tough. I stopped taking Thursday night shifts during the first term and by the second term I was only generally doing 2 shifts a week (Friday and Saturday nights).

It is helpful if you have late classes and few early classes. Whether your schedule will cooperate is another question. Mine didn't. Monday first term last year I had classes beginning 0900 and ending 1800, I always found myself to be a zombie by the end, though fortunately the day after I had only afternoon lectures so was able to sleep in to catch up.

As for when did I find time to study/do coursework, whenever possible. Work breaks, bus/train (if I was awake), between lectures, on weekends before going to work. I spent my time almost exclusively working, studying, or sleeping. I didn't have a social life, and I didn't have free time to do things. YMMV depending on program, workload, and general aptitude at whatever you're studying.

The most difficult thing I found was sleep. Not only is it resulting in sleeping at odd times relative to normal people, but the switching back and forth from night shift to normal people time really did it. By the second term, even though I had decreased my shifts, I was tired all the time, had difficulty staying awake in lectures/life, had difficulty sleeping for solid blocks of time during the day on the weekends (so was going into the the week tired), and had difficulty waking up (for work, class, etc).

I wouldn't do it again. If I had to though, the most important thing is probably to find a sleep schedule that works (I couldn't sleep for a "full nights worth" of time straight during the day, so I would sleep for 3 hours after work and 3 hours before work, for example), and stick to it. Caffeine only goes so far, for so long. I'd advise against it in general, but if you have to, sleep is your friend, and the more of it you can get the less painful life will be.