Replacing Content in Video

Show us the video you are trying to work on. I have replaced objects in an actor's hand. Some shots took a couple of hours, and some took a couple of weeks. It all depends on the shot. The more prep you make and the better the execution of the shot, the easier it is to replace or add any object to any scene.

Replacing stuff in video requires proper preparation for tracking, keying and so on. That's why you see all those red dots on the walls and green/ blue painted stuff in "making offs". The rest depends on the specifics of the shot, which can only be determined by actually seeing it. There is no one fits all technique. Some things are simple, others infinitely complicated.

Mylenium

Moved to After Effect: check out rotoscoping.

You might try the Premiere Pro forum to see if Premiere can do that — or we can move your post there. 

Jane