Hi, I did my best to find the user manual for this hair dryer, but it's not made anymore since it's an older model and I wasn't able to find anything. Sorry about that.
That said, there's really not much to it. There are two fan speed settings, Low and Hi. Hot air blows unless you're holding down the "Cool" button. That's about it. Also, if you're traveling abroad to a country with 220V outlets, you need to rotate the power input switch to 250. In the US, it should be set to 125V.
As far as which brush accessory to use for what purpose, I really don't know about that :(