BT works, but it cannot dump all the can packets from your car as it's too slow. The idea is the MCU processes the packets and uses BT to send sensor data or whatever to your phone. I'm implementing stuff in the firmware to filter packets on the MCU so you can get can over bt if you know what message id you want. But out of the box you can use BT to talk to the MCU and send commands with a generic BT LE app like Lightblue for iOS. I'm yet to find a good one for Android. The docs list some of the BT LE characteristics and what they do.
On the USB Serial thing, I'm willing to bet whatever software you're using doesn't recognize the USB vid/pid. I had to wrestle with that in the mobile app to get it working. But USB serial to android does work.
Still working on all this software so it will get easier soon, and still be open for people who wish to dive deeper.