Canuck WordPress Theme is doing very well.
With that, comes many requests for customization of the theme. If you don’t want to change too muck, the best way is through the Customize -> Add Custom CSS panel.
However if you want to make more extensive changes, it is best to do that through the use of a child theme. I have set up a starter child theme and it is available here: Canuck Child Theme Starter.
It has taken a fair bit of time to set this up so I am charging a small amount of $10.00 for the download.