How long should the streamer be 12 or 24 foot. The streamer will have the bird in it. I will throw the streamer and then produce the dove. I can't find any video that show this in action. They all do steals. I want the bird to be in the silk streamer I throw out. Thank you

Usually they are 12 feet long...

A 24 foot silk streamer would be difficult to handle. After tossing it out, you have to retrieve it. You can pull back about 3 feet at a time which would mean you'd have to do a retrieving motion about 8 times, ending up with quite a bundle of silk. For that reason, a 12 foot streamer would work better. I'm assuming you don't do body steals. Having the bird in a pocket in the streamer might be a little difficult to handle. You'd have the bulk of the bird itself plus the rolled up streamer.