"Bueno, buena, buenos, buenas, buen" are not”verbs, they are adjective. I'm not sure that I understand your question. You can say "Buenas" instead of "buenos días”, "buenas tardes", "buenas noches" but also you can say "hola" when you are coming. When you are going you can say "buenos días", "buenas tardes", "buenas noches", "adiós", "hasta otra/luego/pronto/la vista" but you can't say "buenas" because it is like "hola"