Life is too short to julienne by hand, so buy a tool instead. Many Asian recipes call for the vegetables to be chopped this way—and you will zip through your prep faster if you are armed with one of these. Try out different models until you find the one that has the perfect thickness and size, as there are many variations.
Mandolins can be handy for thinly slicing onions and garlic, and you don’t need to spend a bomb to have a good one. My favourite is the Japanese Kyocera ceramic handheld type. Amazon sells them very cheaply and they also make a julienne version. Both come with a little hand guard and stay sharp for a long time.