Small game and fish I freeze in a ziplock bag filled with water.Deer roasts I vacuum bag, Ground deer quart ziplocks with the air pressed out. I cooked some squirrel this week that was a year old and not freezer burned.
I too use your method with ziplock bags for small game and fish. Would note to be sure you get freezer bags, not storage bags, as they are often mixed together at the local walmart.
