Silky Waters (also possible for 3D) ... How to - step by step - page !!

Summary :

Instead of taking with your standard camera 2 cha-cha pictures with a calculated stereo base, just take 2 movies of about 5 seconds
(generally a small tripod or a flat surface is better for stability but handheld can be used if necessary !).

Replacing costly high quality neutral density filters (ND 400 to ND 1000) and the inherent difficulties of their use (especially the must have of an heavy hyper-stable tripod),
those 2 movies will be easily post-processed with freewares to give a 3D couple !

Requirements : a lot of GB (~ 20) of free space on your hard disk for intermediate steps savings.

Softwares used :
PIPP https://sites.google.com/site/astropipp/
VirtualDub http://www.virtualdub.org/
Autostakkert (to input the AVIs, do the registration and stack into a single resulting frame) https://www.autostakkert.com/
Stereophoto Maker (to make the final stereo couple from the two result images) http://stereo.jpn.org/eng/stphmkr/

Main steps to do with both movies ...

PIPP (in the case your camera's outputs MOV videos and not AVI)

VirtualDub
Loading the AVIs, cutting enough frames at start and end that could be affected by user button press, selecting final frame number

and save as uncompressed AVI

Autostakkert-3

Placing an alignement point on a contrasted feature

Stacking

Final image

SPM

loading both frames

Other examples (right-clic and save full size) :

Handheld with 100 frames !

Auto alignment