The Bsurfaces addon, build in Blender 2.8, creates mesh from annotation strokes. You can project these strokes on a surface. Or you can place stroke relatively to the 3D cursor or view. Meaning that you can use the Bsurfaces addon create meshes or use it for retopology. In this post I show you how you can use it for organic modeling. Here are video which makes it easier to explain the workflow.
There is not much more to add at the moment because it looks like the addon is still in development for Blender 2.80. Though, a workflow will be added later on how to use the Bsurfaces for retopology. In case you have idea’s or suggestions, let us know in the comments.