Jim,
OBS may be an option worth exploring. It is an open-source video recording app for the PC. I assume you record guitar and vocals through an AI (Audio Interface) into waveform12. With OBS you’d be able to source the audio from the AI and using an add-on to OBS continue to use your phone as the camera (explained here).
I like this approach as once the sound setup is done, then there is no need to do any post recording editing. Many people keep the video as it was recorded ie from the moment of pressing record to hitting stop. The next step is to trim the video to make the video start and finish with the performance. You can then add some text up front, usually a song title to start and a thank you to finish. I expect that would be quite easily done in Resolve without needing too much study of the manual or tutorials.