I've got some rotating brushwork, and when it flips upside-down, its not lit properly anymore. I've been messing around with a light_dynamic, but I cant seem to get it to cast a spotlight. I just managed to get it to light the brush its sitting on, but it didnt light up properly.

Any ideas? or will I have to use a work-around with static lighting?

Source Engine lighting is static, you can't achieve that without a dynamic light, but these lights are far too expensive to be taken seriously. Try messing with the minlight or lighing origin properties (if any). If it does not work, you can try the light_dynamic, it should be used like a light_spot, but be careful not to light a large area with it.