My flaring tool is the same as Al's one. I've tried a few different ones in the past, but that one is far and away the best. :edit: It also handles the original steel pipes as well as the replacement copper. Not all do, so buyer beware!
Of course I practiced mutliple times before I ever went near a car with it, but to be honest it's almost impossible to get wrong with that tool. The only mistake I made that first time? I forgot to put the fitting on the replacement section before doing the second flare! Fortunately I had enough slack to cut off the end and do it again...
:edit to add: When replacing sections of pipe, it's my opinion that you should use as few connectors as possible, since each one is a potential point of failure. If your issue is near the rear of the car, consider going all the way back to the flexi hose union. Copper is (relatively) cheap after all, and there's nothing to say that a section which looks okay to join to now, might go scabby in short order.
Incidentally, the Swiss MOT (which is noted for being a complete pain in the backside) actually doesn't allow for any additional unions that the manufacturer didn't install. Scabby pipe? You're replacing the lot, from the ABS unit back.