Blueberries, just like other fragile berries, should not be washed until you are ready to use them.
To tote these parfaits to a picnic, assembler them in disposable paper or plastic cups. Look for cups and lids at a party-supply store. Pack them in an insulated cooler.
Prepare the parfaits, cover and refrigerate them for up to 4 hours. Just before serving time, garnish the parfaits with whipped topping.
To make Blueberry Sundaes, serve the blueberry sauce over ice cream.