I work for Head Start and do this activity with families in their home.
I arrive with bird seed already measured into quart size ziploc bags. I also have the yarn already tied onto the top of the pine cone. After the child spreads peanut butter over the pine cone, he can unzip the bag. While Mom holds the bag open, the child lowers the pinecone into the baggie, leaving the yarn hanging out at the end of the zipper. The child zips the bag closed then shakes the bag to cover the bird feeder with seeds then gently sqeezes the baggie to set the seeds into the peanut butter. Bring the bag outside,tie the yarn to a branch, unzip the bag. You will still have bird seed left in the bag,just hang on to it. When the child notices the pine cone is empty, bring it back in and do it again. :)