There are some blur examples here https://github.com/subsoap/deffx/tree/master/deffx/materials/rendertarget
Here is another blur shader made by someone else https://www.defold.com/community/projects/125545/
There are more materials here
FXAA Render Target example + FXAA
Keep in mind with all things material if things don’t work right check the builtin materials for breaking changes that are possible when using other stuff a few years old.
I still have work and plans left for the book and stuff beyond it but I’m focusing on gamedev right now. Will probably focus on this again after the next game is done later this year!