It's actually super easy.
Prerequisites:1. External drive that is always "on". I have my Seagate plugged into a USB port so when I boot up it's on.
2. Download and install this application so you don't have to mess around with any syntax command line nonsense:
https://schinagl.priv.at/nt/hardlinkshellext/hardlinkshellext.html#contactCreating a "Symbolic Link":
Step one = create folders * on your external drive and
MOVE your "Skin" folder to it - deleting the "Skin" folder from the "Paint Schemes" folder
Step two = right click the Il-2 1946 "skin" on the
EXTERNAL drive and select "Pick Link Source"
Step three = right click anywhere inside the "Paint Scheme" folder and select "Drop As" then "Symbolic Link"
Step four = check to see if all worked out - you should now see a "Skin" folder with a little green arrow on it signifying a symbolic link.
...and that's it!! Everything in game works the same way and this adds maybe a second to mission load times.
* I created a "Skin Storage" folder and 3 sub folders for 3 different sims and placed their "skin" folders in their entirety inside:
IL-2 Great Battles
IL-2 1946
RoF