all these suggestions should be fine - here are a couple more
in vertex mode, hold down shift and control then drag your mouse around sections of your track to select the vertices from which you can then Vertex->create-ordered surface. This way you can create large polygons in one go, rather than making loads of quads/triangles individually, which takes a while.
You might also try using Vertex->create-2d-mesh which will create triangles between closest vertices. Depending on the shape, you may be able to do this on your whole layout and then delete the triangles you don't need. Otherwise, doing it in sections will be better. This is the one I'd try first.
Andy