I've got waze on mine. It wasn't an overly difficult process.
(And I know what you mean with Garmin; I've had issues with it giving awful short cuts)
An abridged walk through:
1. If your head unit has been updated, use the settings to restore to factory defaults.
2. Navigate to CMDroid.com on the car's browser. (There is a menu at the bottom to translate the page to English)
(You can either follow their how to (Google translate the PDF's))
3. Download your chosen App (They recommend the older version of waze for stability); It can now be installed by opening it under the downloads menu - Only one at a time though; to install multiple, the previous download must be deleted.
Install waze & "Permissions" (Top left)
4. Set permissions for Waze. - You can interpret this PDF into the UI http://www.cmdroid.com/documentacao/...Parametros.pdf
Use box 1, with the process & package name com.waze
You can get a list of the process names for other apps here too CMDroid
That's something of an abridged version of what I worked out myself in an afternoon, so that should do it for you.
You will have to connect your car's head unit to your mobile hotspot whilst driving, just as a heads up, unless you use one of the other apps, like sygic which offers off line navigation (More involved install though!)
If you need any assistance, let me know