If you have a dog doing a "high five" it's an easy step to waving goodbye (something all my dogs learn).
I use the command "bye bye" (which sounds similar to "high five" with the long "I" sounds). I just gradually move my hand farther away so that when the dog brings the paw up, it doesn't actually meet my hand. And then I praise and reward. Over a period of weeks I move back farther and farther until I don't have to be really close to my dog, and they will wave the paw anyhow.
Every dog I've done this with has developed their own distinctive style of wave. Some really bring the paw up high, some slap it on the ground a few times, some wave it up and down like a true wave. It's really cute to see how they develop their own.
As long as you're working on paw exercises, you can do some that involve a dog rubbing/covering their nose/face with a paw. I usually teach these with the dog laying on the bed with me .. *L* .. but you could certainly be on the floor with the dog. Some people use a small piece of tape that they put on the muzzle so that the dog brings a paw up to rub it off. I just blow very softly on the dog's face and all of mine have responded with bringing a paw up. Then you immediately mark and reward that behavior. When the dog is doing it consistently with just a small puff of air, I add a verbal command (or signal, or both) and then I fade out the puff of air.
This is another one that they tend to develop into their own. Khana will hold her paw over her eyes, even at a sit. Trick lays on her side and covers her nose. Dora reaches up and rubs her nose quickly. So with Khana I ask her "are you embarassed?". Trick's command is "what stinks??" and Dora's is "does your nose tickle?".
Teaching tricks is great fun. I used to take the dogs to do performances at the fair so we had a ton of tricks that we did.
Melanie and the gang in Alaska