I am having a lot of trouble trying to do both at the same time.
the thing with singers who play guitar, is that they usually play rhythm and not lead, so they can focus on singing and playing, but it wont be as crazy as the lead guitarist, there IS some singers who play lead and sing as well, but it takes practice, and you mostly have to have the guitar charts memorized ( like you should anyway ) and the singing charts, pitch ect. and with some practice you’ll get alot better at it