this has always been my favorite way to really denoise a image + really arrange the image better…and now my plug-in is old, and I can’t seem to find a new one…ughs - if you know where to download one safely for win10 (64), please let me know.
It is now part of the GMIC plug in. The GMIC plug in has lots and lots of filters. In the Repair menu Smooth [Anisotropic] is essentially greycstroation IIRC
actually, I’ve found out greycstoration still exist - as a separate plug-in (like gmic) …you add it in your plug-ins and put it in through gimp that way (via plug-ins) -just look up/google GREYCstoration.com