I'm making a Cellar Craft Old Vine Zinfandel 12L (with grapeskins). The instructions direct to either stir 2x daily or weigh down the grapeskins (in a muslin bag) to keep them wet. Because I'm lazy and don't want to risk infection, I don't really want to stir the mix. What can I use to hold the bag under the surface? What do you use?