Another collection of seven dailies from the Facebook Page!
A technique for using Gimp:
Instead of using a brush to apply something, duplicate the layer you are working on (right click the layer in the layer list and it has the option, or do Ctrl+Shift+D).
Change the filters and settings on the copy, then put the altered layer below the original, and use the eraser brush on the original.
I have found this makes a vastly smoother gradient for some reason, and because the eraser has the anti-erase option you more or less do not have to worry about running out of or confusing undo steps. This also allows a brush to be used to apply changes that would not otherwise have a brush option.
You can also try different effects while keeping the same brush pattern, by making multiple duplicate layers and altering them differently.