Chromecast always uses Google's DNS servers so you can't just change DNS server on your local network, you have to redirect all DNS requests to another server. This guide will help you do so with a OS X computer and a phone.
Requirements for this guide:
- Phone with tethering
- OS X >=10.9
- unblock-us.com or another DNS resolver
Steps:
- Tethering your computer through your phone, eg. connect to your wifi, and tether with USB.