I have made some changes on ~/.xinitrc, then you need exit from openbox and use startx again, after plug USB Keyboard... and why not use a automatic method? well in my tests... if I apply a .map file on a running Xsession... the keymaps go wrong and many kays dont works, I dont know why this it....
The files is here, I think you need change some thinks in abnt2.map, this is for Brazilian Laptop Keyboards.... for get keycodes use xev