Surprised you put this in GD!
The Kevin Richards videos on
Rock the Stage NYC channel have been the most helpful in terms of explaining and describing the techniques required to hit those rock god notes. Its hard to find truly inspirational teachers because they are explaining entirely internal processes.
Given you are a guitarist, you can, like me, use the same methods you learn guitar stuff to train your voice. Mic yourself up, cut the low bass, compress and reverb, google karaoke/instrumental versions of songs you know and try singing them. Let your musical ear guide you.
For the longest time, i couldn't figure out 'falsetto' and the higher notes, always straining at the top, until i realised falsetto is just singing in a monty python female voice. All you have to do is sing in that and work backwards, working out how to connect it to your 'chest' voice by 'yawning' it back. I am still confused between chest, head and falsetto because the information online is conflicting.
Also, what are your goals? Do you want to increase your range? Is there a specific type of music you want to sing?
AC DC - you shook me all night long is a surprisingly easy song to sing falsetto.
Jeff Buckley/Leonard Cohen - Hallelujah has a pretty easy reach chest voice range.
and as hilarious as it sounds, 'Let it Go' from Frozen is a really good connective song because the verses are in chest voice and the bridge moves up to the chorus in falsetto