front brake. seriously. if you have a hill you can't negotiate with your legs, get a brake. it beats barrelling through a stop sign at the bottom and getting creamed by a ford aerostar.

now, if you're totally dead set against that, the other option, of course, is to go for a smaller gear. swap out that 17t for a 19 or so. your top speed will suffer, but it will be easier to slow down too. maybe try walking your bike halfway down the hill and riding the rest. then the next day start 5 or so meters further up the hill and just keep doing that til you're confident with your ability to do the whole thing brakeless.

or just get a front brake and enjoy your ride.