Select everything except ears from mesh of head I have a triangulated mesh (100k+ vertices) of a head.   I need to select everything apart from the ears, and reduce the vertex density on that selection by 16x or something.

Here is what I'm dealing with: 



I've already asked a question on how to do that and got a very helpful answer: Reducing vertex density as distance from point increases

My problem is selecting the ears.  I would like to get a high level of control; simply using box select isn't going to cut it.

So I select a vertex path around one ear:



Now I'm stuck, can someone guide me?

What are the steps I need?   This is my guess:


somehow store the vertex-path
do exactly the same for the other ear
now might there be some tool like Microsoft paint's flood-fill,  where I just hit one vertex on the skull, and it will select be entire skull up to and including the boundaries I've just created (i.e. it will avoid the ears)
then I decimate, which I have instructions for


Is there some tool I can use that will just let me draw on the surface, and then  it will figure out an appropriate vertex-path?   when I do this on a 2M vertex model, it is going to take ages manually clicking 500 vertices.

EDIT: I got one step further:
Another way: If you don't mind adding some extra points on the model, you may also consider to separate ears by cutting them off using Knife Cut or Knife Project tool:





PROS: Almost perfect clean separation.

CONS: Add extra vertices to the original mesh. You may judge and weigh if this is acceptable.

Then CtrlG to add those vertices to a new group for the restraining usage in Decimate modifier panel.