If you want to make real traditional French sour dough bread, this book is the best I have ever tried:
www.amazon.com/Bread-Alone-Fresh-Loaves-Hands/dp/0688092616You can get it used for $2. The Chapter on Levain and the recipe called "My Personal Favorite Pan au Levain is the best bread I have ever tasted.
The hard crust is not as big a problem with really fresh bread and slicing it thin eliminates the problem. The book details how to make and maintain your own levain(sour dough starter). It involves a tiny pinch of quality yeast to help along all the natural yeast and bacteria present in flour and in your kitchen. The starter is sour but the finished bread is not the overpowering sour of the SF variety.
Warning this is an all day project to make the bread after you spend 3-4 days brewing a starter but worth it. Unfortunately you can't make sour dough bread like this with 100% whole wheat. You just don't get texture and varied air bubble size in the loaf. I usually used 3 white to 1 whole.