could be that the image you're filling with the paint bucket is too big. I usually like to create an image 1000x1000px and then crop or resize.
Is there anything else running in the background that might be slowing you down? Apple support, quicktime and other stuff like that doesn't need to be running all the time. (I don't know if Macs have things running like Windows does)
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That is my spot, in an ever changing world, it is a single point of consistency. If my life were expressed as a function on a four dimensional Cartesian coordinate system, that spot, from the moment I first sat on it, would be 0-0-0-0.