that's cool, but I use (IMO) an even easier method, a contextual menu plugin
called FinderIconCM
for those that don't know, a contextual menu is what you get when you control click or right click. using this, you can copy/paste icons, and create or edit icons as well.
Copy paste the pic in preview or whatever then copy and paste it (command C), select the app or folder and file: get info (command I) then click on the pic for the app/folder you see and paste (command V)
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