Aluminum bonsai wire is very useful. When you bring you bonsai out of their winter storage you may find an excessive amount of moss. If moss covers the entire surface of the soil it will limit the flow of air and moisture to the root system. And if the moss is growing up the trunk of your bonsai the result is usually fatal. Thin the moss to allow air and moisture to penetrate to the root system and remove all moss from the tree trunks.
Spring is a good time for spring cleaning.
Take an old toothbrush and a mild soap solution to gently scrub the trunks of your smooth barked trees. You will be surprised to see the amount of grime that is removed. You will not only remove dirt but also bugs, fungi, moss and the same time stimulate the tree. Inspect each of your bonsai carefully. Be especially alert for old wires.