Coherent usage of Hibernate's session and DAO
Instead of working with Hibernate sessions, I encourage you to use the JPA API. I think this is the most common way to work with Hibernate now. (http://www.theserverside.com/news/2240186700/The-JPA-20-EntityManager-vs-the-Hibernate-Session-Which-one-to-use)

For the transaction aspects and the initialization of your DAOs, I also think that a solution like Spring (http://projects.spring.io/spring-framework/) would help to simplify the code of your application.

Your code would look more like the following (with annotations stuff):

public class MyService {
  @Resource
  private AModelDAO aDao;

  @Transactional
  public void something(object) {
    // no need to manage transactions or sessions here
    aDao.save(object);
  }
}