GIMP - New in the development branch: the Smudge tool can now sample colors from all visible layers, so you can smudge on a separate layer and keep the original data untouched.
Smudge Tool question
rgb - In GIMP, how do I get the smudge/blur tools to work properly? - Graphic Design Stack Exchange
Getting The Smudge Tool Working In Gimp 2.10 - artloader.net
3.16. Barbouiller
3.14. Smudge
GIMP 2.10 Tool Preset Fixes by PkGam on DeviantArt
3.16. Smudge
Smudge painting — Tutorials — gimpusers.com
Smudge painting — Tutorials — gimpusers.com
Solved: Smudging Jitter tool ? - Adobe Community - 9497954
How to Use Smudge Tool - GIMP tutorial
Smudge tool changed! (2020) — Help & Support — gimpusers.com