Day 122
Doing some experimentation and research.
You can make a variable ND filter from a Linear polorizer stacked with a Circular polarizer. Linear has to be toward the subject, circular on the camera side. Works better with some lenses than others. And at the darker alignment of the filters, there is tremendous color shift. Also, at least with the filters I have, there is a great deal of vignetting with wide angle lens.
No adjustments were made to the photos other than creating this composite image.