Look for an abandoned paper wasps nest. They are about the size of a football or sometimes a bit larger. Tear off a piece of the outside (more waterproof than the inside) and roll it in your hands until you have a tight ball a little larger than your bore. Pour your powder down the bore and drive the wasps nest down and then your patched ball. Make sure you seat your ball firmly on the charge.

The oldtimers used it to seal the bore from moisture and protect the patch. It works much better than corn meal. It doesn't burn very well; try it with a lighter and you will see. A bore button is the best option be cause it can be lubed and seal the gases a bit better. Your accuracy will improve with either.