No tips what so ever, but I watched James Keelaghan a couple of weeks ago at Llantrisant Folk Club in Wales, he was singing a song when he broke a string and as far as I can remember he continued singing and was back playing guitar before he'd reached the end of the song and I don't rememeber it having 100s of verses!! He used a little windup jobbie to tighten the string.(sorry to be so technical)

Stunning performance all by it's self.