The crayon tool should automatically be set to spread and noise to begin with :/. Are you sure you're using the right tool? Some tools don't have the option. Or is it the blur tool?
Hmm. I have version one of Sai, so this doesn't make much sense :/. I honestly don't know what to tell you. I actually had the same problem with my friend's square brush settings. There are no square brush options in my version. Neither of us can figure out why. You should probably post a question about it in the forum. If you get any answers let me know and I'll post it in the description.