I would create curves over your pic like a path and use a profile (circle) and extrude it along the path. this way you get a even distribution of your geometry. you could also break up the extrution and do a second one right from the beginning of the spiral and use a scale of 0.7 or something to make it thinner in the end.

after the nurbs oart is done, convert it to poly and refine the geometry.

be aware of normals before you combine geometry.

gl!