Since it turns out that some people do not have start-sai.exe and DA doesn't permit to include .exe files in uploads you can grab it here sta.sh/0rtidxox7i6
0. Exit Sai if it's running
1. Place start-sai.exe in your main Sai folder
2. Place textures in brushtex folder
3. Use start-sai to run Sai
WARNING: Sai supports a limited number of active textures. If you already have a plenty of textures installed and some of the textures do not show up, I suggest you place some of the textures you won't be using into an archive or a separate folder, so that you can get them back when needed.
You can view long strokes here
These work with all tools. Changing the size or hardness/softness of your tool will produce a different effect each time, so play around.