Right, @Mr-Quebec. I presume the reason for “blurring” is for noise-reduction purposes? If so, there are certainly more “user friendly” ways of reducing noise than manually adding masks and Gaussian blurs. 🙂
For example, the GREYCstoration plugin. (Download the .zip file, and extract it, then copy GREYCstoration_gimp_pc_win32.exe to GIMP’s plugin folder. Usually located at “C:\Users\Your User Name\.gimp-2.8\plug-ins” Restart the GIMP, and you’ll find it in Filters>Enhance>GREYCstoration )