It would be nice if you could add a guest to a Sketch Cloud project so they can see all files within a project. It becomes tedious to invite guests to individual files, which seems to be the limit to what you can do with guests at this time.
@sonburn We hear you!
We’ve recently been investing time in reviewing the sharing options available within workspaces, and the ability to invite guests to projects is something we’ve actively been working on! We hope to able to ship this soon 
So keep your eyes peeled on our newsroom category here on the forum, or our social media accounts for any future announcement! 