Once the eggs are hard boiled, put the cooked egg yolks in a zip lock bag. Seal it up, mash them up until they're all broken up. Then add the remainder of your ingredients, reseal, keep mashing it up mixing roughly, cut the tip of the baggy, squeeze mixture into egg. For an easy clean up, just throw bag away when done.
Read about that tip here. Just a devilishly good idea. (I know, I know. Boooooo!)