Permanently enable to show hidden/system files when searching in Finder

Per the tutorial,

• CMD-F to bring up the Finder search window.
• Make sure "This Mac" is selected.
• Click "Kind", choose "Other...", and double-click the "System Files" entry.
  Update: if you click the "In Menu" checkbox to the right of the "System Files" entry, "System Files" will also be added as an option in the "Kind" dropdown list.
• Click the "aren't included" dropdown, and select "are included".

This time, though,

• click the "Save" button at the right, just under the "Search" box.
• Change the default name to something descriptive, but short, like SearchAll.savedSearch.
• Make sure "Add to Sidebar" is checked.
• Click "Save".

Now, when you want to search all the files:

• Click on the "SearchAll" sidebar item.
• Enter your desired search term (such as Helvetica, as in the tutorial).
• Click "Name matches", if that's what you want, or press Enter.

Voilà! Now you can easily search even those hidden/system files!

To see hidden files

defaults write com.apple.finder AppleShowAllFiles -boolean true; killall Finder;

After the above command, relaunching "Finder" is easiest with the KillAll command. So:

defaults write com.apple.finder AppleShowAllFiles YES; killall Finder;