I remember seeing a video back around Blender 2.6x-ish where the grease pencil was used to draw on the surface of a model to retopologize it. Is that something that's still doable?
Solution: Yes. It is. There's an add-on for that. BSurfaces GPL Edition installed by default in 2.8 but not activated.
spikeyxxx ... does that allow you to create a mesh from the grease pencil marks?
No, I misunderstood your question. For that Bsurfaces is needed like you said.
But I am quite sure that that was never possible without that addon.
