DON'T BRUSH YOUR HAIR.
I know that sounds weird, but I have the same kind of hair except curly. Frizzy hair is better off either very long [its weight holds it down] or very short [very easy to manipulate with gels and such], a decision to be made based on your features and such.
- keep it trimmed regularly and have it done dry so you, or whoever does your hair, can see what it wants to do.
- don't be fooled and use too much product. all you might need in the winter is some serum and in the summer, some gel*
- avoid heat styling. if you can get the same effect by wet/damp-setting your hair as opposed to using a flat iron** or curlers, get used to that little bit of inconvenience and your hair will prosper.
- you can brush it to get it into the set, but once you take it out, don't do anything more than shake your head a little and arrange it with your fingers without raking them through all the way. Separating the hair from it's style by brushing seems to "confuse" it and it doesn't want to go back.
* I have very long hair [waist length] and I wear it "beachy" so I can tolerate humidity without having to wear braids or bun all summer. I put in gel while it's wet, let it dry, then set it all night. All I have to do when I get up is shake my head and spray some gel on it.
** I can indeed set my hair at night so it will be straight in the morning...It may look silly, but it works once you get a feel for it. Pull your hair back into a ponytail [not too tight], slick back any problem spots on the side, put an elastic every 2 inches or so until the end. Sleep in it and remove the elastics in the morning. If it's still not straight enough, all you may need to do is go briefly over it with a flat iron.