Before reading on remember to put the line at the bottom of /etc/sudoers as from experience what happen is that other rules cancel out what you have added.
If your sudoers setup is correct it will work immediately upon saving without requiring a reboot.
Edit /etc/sudoers
yourusername ALL = NOPASSWD: /path/to/command
*Once again remember the above should be on the bottom of the sudoers file or........