At 8 weeks old, if you want the tail docked, you need to have it done by a veterinarian. She needs to be anesthetized to have the tail removed now.
"Banding" the tail is inhumane in my opinion. So is docking a tail at this age. There is no reason to do this. If it wasn't done at 3 days old, I wouldn't bother. You are just doing this for yourself, the dog doesn't care if it's tail is short or not. Why put your pup through this painful surgery? There can be many complications at this point also.