paint, but there's a couple of tricks that need to be kept in mind to keep it from bleeding through (i learned the hard way )
Use good tape , like Frog Tape --(there are probably other good brands --) - tape off your stripes, then lightly use a brush to brush along the tape line - this effectively seals the tape to the wall without oversaturating it, then wait for that to tack dry and go back in with a wienie roller and fill in the stripe --- in theory, when you yank the tape - you should have a clean line
Note-- i wrote that i learned this the hard way, but i have not corrected my own mistake yet - so these instructions were paraphrased from a DIY program i saw and they described how to do this --- maybe some of the other guys/gals on here who have BTDT have even better advice than that