Kinda having troubles getting this to work.
So I select both curves and a mesh, hit edit mode [for the mesh], but it says No Strokes added to the object.
Sometimes it works, sometimes not so…
Could anyone please have a look?
bsurfaces test1.blend (425 KB)
Not to mention getting Grease Pencil to work is really impossible for me 
Hey, the grease Pencil is working now… Blender works in mysterious ways on me …
Hi!
Openfile, hit Tab and press CreateSurface… There should be one Curve and one mesh object selected; Edit mode for last selected mesh - Bsurfaces works.
Concerning Grease pencil - its all the same - there should be mesh in edit mode and some selected verts if you want to continue mesh, draw line- D key, click Create.
Rotate viewport or have another, perpendicular view open where you mark a depth for GP line using 3d cursor position (set in GP tab on T panel, Stroke Placement=3d cursor).