I have worked on a few different shows that required "roast bird" . . .
One of the methods we have used is (yes, this is a little scary, but it works very well) to first roast an actual bird. Afterwards, prop it so that all grease, etc. drains away. Then, rinse out the inside with soapy water. Obviously you have to be careful with the outside so that you don't mar your work. Next, fill a bucket with shellac, and dunk that baby. Let it dry fully, then dunk it again. Not only do you have a realistic looking turkey; it can survive a few drop-kicks as well!