#1: Smash every vase you see, even if it takes you a little out of the way. It'll save your boredom later.
#2: Once you've unlocked Mill Hill, you can run along the Serfside/MH transition for seven vases, then to the keycutter Serfside/Splitwood Village transition for another five. This twelve vase run seems to be the quickest way of doing it.