A professional teeth cleaning didn't help that much? That seems weird... I hope the vet knew what he was doing? lol. Because usually they get them pretty darn clean.
Brushing is the best IMO. I worked hard to desensitize Jackson, and he still hates it, but he just puts up with it now. I can't do it for more than 30 seconds but at least it's something. We use CET toothpaste and a baby tooth brush.
Check out HealthyMouth ... it's definitely pricey, but it's one of the only approved (by the VOHC) water additives. They have a gel as well that you can rub onto the teeth and gums with a q-tip but the water additive is probably easiest.
Never used Greenies, so not sure if they actually help. We feed Dentastix occasionally (which are "bad", too, meh). But to be honest, I think they make a little difference. My dads dog has nasty breath and since we've been giving her Dentastix, it's gotten much better.
They do have RX kibbles for teeth problems, if her teeth are that bad. As well as foods you can buy without a prescription, like this:
http://www.hillspet.com/products/sd-...-care-dry.html