How to occasionally open a dozen images in FotoSketcher on Windows 10?

Occasionally I want to "oil paint with texture" a score of JPG files.

I can temporarily change the default for JPG files to open multiply
selected files in FotoSketcher but that has the problem of having to
doubleclick on each file one by one and the problem of how slow
FotoSketcher is to load.

Ideally, I want to select a dozen to a score of files, and just open them
all in either one instance of FotoSketcher (like I can with gVIM) or, if
FotoSketcher can't handle multiple files in one instance, then I'd like it
to open a score of FotoSketcher instances, each with one file loaded.

I would think this need is of general use to any photo editor user on
Windows, where they want to open DIFFERENT programs depending on the need.

Any suggestions for how to accomplish that multi-file editing task?