There are no plans as of yet to improve Solder documentation. It is noted multiple times that using Solder in its current state is for advanced users only because I just don't have the time right now in its rapid state of development to sit down and make it incredibly user friendly. (I will do this eventually, just not yet)
As to your issue, I think a lot of people are misunderstanding what you put in for mirror_url and repo_location. If you are using a remote address for your repo_location, your mirror_url should match it. Nothing has to put to where Solder is. Solder knows where it is.