When you're wanting to cast your phone screen to your Hudly Wireless but want your audio to play through your car via bluetooth, a simple protocol will allow you to do so and override Apple's default system which tries to cast both sound and visuals to the same place.
Step 1) Connect to your Hudly Wireless as normal
Step 2) Open the Bluetooth menu on your phone (Settings > Bluetooth)
Step 3) Connect to your vehicle's Bluetooth audio
And now your audio should be bifocated between your vehicle and Hudly!