thats the main reason i don't encourage people to teach their dogs to shake...invited unwanted paws at a bad time
i've found one of the best things to do with unwanted behavior is to make them not like to do it...
example...when my GSD paws, i grab it and hold it a tiny bit higher than she would normally. not enough to hurt her (would never do that!) but i hold it there for several seconds after she tries to pull away. its slowed her down quite a bit.
she used to put her mouth around my arm (not biting, she has a very soft mouth, but more claiming it as hers or something) to let me know she wanted attention. what i did was push my arm back a bit into her mouth where it was uncomfortable, then hold her mouth there for a few seconds. she would try to get away immediately, and i wouldn't let her.
i only had to do that 2 or 3 times before she stopped completely. i've found that this works better than saying no in a lot of cases.