Ive noticed that some bearings will just remain noisy no matter what you do, and if it bothers you replace it with a new one. Like was already said above, clean and lube them. I myself use 91% isopropyl alcohol, spin it on the end of a pen, and blow out the remaining fluid with canned air. I then get a pin, get my bottle of thin lube and let a drop form at the end of it. I then take my pin and attach a small amount of that drop to the tip (whatever sticks, like 1/4 of a full drop, maybe less), and then apply it directly to the ball bearings. If I have to de-shield, I always let them remain de-shielded (the bearing isnt exposed to the wild like it is with a skate bearing, so it doesnt matter imo).
You can decide to use your bearing without any lube. Bearings spin longer with less resistance, and without lube a fully functioning bearing will spin longer. The oxidation of the metal ball bearings may ruin your bearings over time with this method though, so beware.