Skill. Heart. Soul. Oh, all that, and tube amps. Most of those old players had no choice but to make their own instruments. Things like the diddly bo and banjo were just extensions of folk instruments from Africa. There are variants of the diddly bo in South America, the Caribbean, and Asia as well. Story has it that slide was "invented" by some kid playing with either a railroad spike or a pocket knife on his diddly bo. Muddy Waters, as the story goes, learned by tying old bits of inner tube to the side of a barn and "playing" with that until he got a real instrument. There were diddly bos, fiddles, guitars, basses (from washtubs here in the US, from tea chests in Britain), dulcimers and myriad other home built instruments. There's a lot of satisfaction to be had from DIY projects. Desperation and ingenuity can go a long way. Where you once were able to find cigar boxes free for the asking, tobacconists now charge for the nice wooden ones. I got a few from a buddy who smokes cigars constantly. I still have the box from cigars I bought for my wedding 42 years ago. I gave out cigars when my daughter was born in '89---and was the last one to do so AFAIK. End of an era. Check out guitarist Scott Ainslie. I got to work a show with him years ago. He's a blues guy, plays a '37 National, and is a proponent of CBGs. He also has a good repertoire of musician jokes.