When preparing paintings and pictures, each item is to be individually wrapped using 2-3 sheets of white paper.
Although it is not advisable to pack more than one picture per carton but you prefer to save money just add cushioning material between each picture to protect the picture or the glass. Place the picture inside a cardboard box.
Pictures that are to big, wrap them in white paper then cardboard.
Bubblewrap can be used as a protection but it may cause the pictures to sweat and may stick to a picture.
If you have an expensive painting these should be placed into a purposed built crate.