Two good options would be to shrink wrap using Kangaroo or use the Dendro plugin (attached is an example using Dendro).
There are a couple of issues with your file that will make things more difficult.
First, the scale you are using is massive. You model is several kilometers wide in the model space. I worked around this by scaling it down x1000 and back up again but you should just use a smaller scale if possible.
Second issue is that you have over 3000 individual brep bodies. You may want to bake out, do a boolean union operation and bring it back in to Grasshopper to make things run smoother.
Thank you. You are very nice!