Winterizing raised beds for lilies in Southern Wisconson or anywhere along an east-west line laterally is pretty much care free. There are a couple 'key points' that should be followed, however.
1. Do not apply the winterizer mulch until the ground is frozen hard enough to support you without breaking or cracking the frozen crust. For locations like Southern Wisconsin that generally is around Christmas time. The reason for wanting a good, lasting frozen soil layer is to keep rodents like voles and field mice from digging down and eating the bulbs during the winter.
2. Keep the winterizer mulch on until later in the Spring. Remember, without mulch, the soil temperature in your raised garden would warm faster than the soil in a regular garden. So removing it too early can result in earlier than usual emergence of noses and an increased risk of frost damage. In that sense, we want the mulch to hold the cold 'in' a little while longer.
The type of mulch materials used is pretty much up to whatever is convenient and available for the gardener.
