Hi, I'm trying to create a security group with members who have edit access to the blog only (they may not edit the other pages). I found this "Blog management" right in the permissions settings. But if I check this and uncheck all other, the users are not allowed to see the admin panel at all.
You'll need to let them log into the backend (Access to Pages Section, tick), or put the blog management widget on the blog holder/tree.
The management widget lets users post from the front end, though the editor isn't quite as complete as the backend CMS one. Specifically there are issues when it comes to uploading images (you can't). You'll also need to create a method for them to log in. A direct link to /Security/login?backUrl=/blog should probably do it, or you could investigate the member profiles module https://github.com/ajshort/silverstripe-memberprofiles