I have written a short guide about adding post-processing shaders to MonoGame, it's a simple guide covering the minimal amount of necessary knowledge that assumes you know a little bit about anything. I've gotten more RTs and Likes on twitter from this post so I thought "hey, maybe I'll cross-post here because people might find it useful".
Here's the post: http://retrocade.net/2017/01/25/post-processing-shaders-in-monogame/
On a side-note, I'll certainly be writing more pieces on MonoGame in the near future as I go through the trouble of understanding some things in the framework and in shaders in the future and I'd be happy to cross-post those posts here if that's fine with the rules :). (and since those don't seem to be written down and I am not a very active user I'd be glad if someone could educate me on whether I am welcome to post those as separate threads or keep one thread for them)