Download the mod:
http://www.guru3d.com/files_details/sweetfx_shader_suite_download.html
Once Downloaded, open zip and move everything to SteamApps\common\dota 2 beta\ folder.
so you should have your SweetFX folder and a bunch of files from downloaded zip in \dota 2 beta\ folder.
now put d3d9.dll and injector.ini from downloaded zip file in
\Steam\steamapps\common\dota 2 beta\bin\ folder aswell
Now you need to download custom settings designed just for dota. ''Preset''
Important to download it and dont skip it !
Download it here:
http://sfx.thelazy.net/games/preset/1092/
It's a .txt file, once downloaded it, rename it to SweetFX_settings and replace with the one in \dota 2 beta\

I recommend having maximum settings in dota 2, and moonbeam weather effect.
Does not affect your FPS.
VAC safe

That's it !



Video of SweetFX in action : https://www.youtube.com/watch?v=do7jDCFd_jI

Hope you enjoy.
Special thanks to /u/zhuoyang for posting this on reddit.