Have you tried a rolled up newspaper? A good swat or two on the behind, along with verbal correction doesn't hurt them, but the sound startles them and diverts their attention from the behavior. This method helped to cure my lab, Chipper, of a multitude of sins when he was a puppy. I've also heard of filling a plastic jug with small rocks and throwing it near them (not on them - LOL) whenever they do something wrong. Good luck!
If you use the command Down if you want them off of something you should use a different command for lie down. I use OFF for get off things. Jetta is really good about not getting on things, but Oscar is of the belief "where theres a will theres a way."
Sophie's a real expert at counter surfing. She will get down when I say no, but as soon as I turn around she's right back up there. I saw Victoria Stillwell (hope that's the right name) use sound diversion to cure a dog of doing that. The trick is to use a quick loud noise that the dog doesn't associate with you, but that startles him and stops the action. You have to be tricky and quick so you can make the noise without the dog seeing you do it. Hope this helps.
Lola was a counter surfer and I just kept telling her off. Now she only does it when we're not looking, but she gives herself away because she plays VERY LOUDLY with whatever she gets off the counter! Just push everything as far back as you can and keep reinforcing the "off" command.