Don't brush wavy hair. I use a flat paddle brush to straighten it or to detangle it before I shower but don't brush it before you go out, it'll just frizz up. While your hair is still wet, use a wide tooth comb to detangle it, then leave it alone.
i have wavy/curly/frizzy hair and i never brush it, i never really comb it either, it doesn't really tangle. i'd say only comb it when it's wet. i use Sunsilk, the green one which is for curly hair and serums are good to control frizz.
how wavy is it? use a straightener with some anti-frizz spray. do you even want it straight? embrace the wave if that's what you want. put a creme mousse through your hair after washing and scrunch/blowdry to accentuate the wave