I tried adding resistors but it seemed to cause my lights to flicker
Ah so you are doing electronics by the trial and error method. Just try things and see what works and hang any theory.
Well there is no substitute for knowing what you are doing. There is no way the addition of a resistor could, by itself, cause an LED to flicker. So you either had something else wrong that you didn't notice and it got corrected in the rewire. Or the flickering is still there but because it is so bright you now no longer notice it. Either way what you should be doing is investigating why you saw the phenomenon and not spreading rubbish round the internet for some newbie to fall into the trap of being miss-informed by you.
Too many people think that if they throw something together that they don't understand and it appears to works then the design is good and it will work for others. A case in point is the shift register tutorial on this site that advises you put a capacitor on a clock line to stop flickering. This is not only totally wrong but can end up damaging your arduino.