Although this seems like a complicated workflow, it isnt.
This is mainly for icon designers. When you create an ".icns" file for the mac (which contains 1024px, 512px, 256px, 32px and 16px versions) and save the file (with icon composer for instance), the file's icon stays on the normal ".icns" file. This means you can't copy the icon and paste it in another file/folder.
Some website tell you to open the .icns in preview, select and copy from there… THIS IS WRONG! it only copies the current resolution in preview, but not all versions. If you look at your finder icons, you will see they aren't the same when in list view or icon view! That's because in list view, icons are tiny and thus would not look great with a big resolution icon
File action on ".icns" files
Keyword "selficon" for currently select file in finder
Download: http://d.pr/f/mPRy