How do I bulk deselect checkboxes in iTunes?

Go to the music folder or playlist you want. Click on any song. Then, press <control>a. This will select everything in the folder. Right-click on any song. A pop-up menu should display and two of the options should be "Check Selection" and "Uncheck Selection".

I think you can figure it out from here. :c)

To me, checking and unchecking items to sync to the iPod is tedious.
Using playlists is much easier to manage what goes onto your iPod.

Try creating playlist(s) and syncing only those playlists.
Select the iPod in iTunes. Click the Music tab.
Tick Sync music and Selected playlists.
Tick the playlists you want on the iPod.
Then just Add/Delete from those playlists and plug in the iPod.

The only time I uncheck things is for items I never or rarely want on the iPod such as old audiobooks and Christmas music.

Command-click on a check box and all should uncheck.

tt2