Hi, I lead worship and sing playing guitar and am working to refine my vocal technique. I realize that relaxing, maintaining good posture and proper breathing technique are all important to really great singing but doing the above while playing a guitar adds an additional factor. Are there any sessions on 30 Day Singer that touch on this topic? 

Hi, Sammy! Here's a lesson series on singing & playing guitar at the same time: https://www.30daysinger.com/tutorial/how-to-sing-and-play-guitar-ukulele-at-the-same-time. 

As for maintaining good technique while you play, hopefully that becomes easier with consistent practice. That's the goal of daily practice: you return to your technique so often that it becomes second nature!