How doe do article distributors who submit each article to many directories get the submissions in when so many article directories require each author to register with usnername and passowrd and email address for conformation?
That depends on which article distributors you are talking about. Cheap article distributors like iSnare.com have an agreement with many of the article directories. This means that the article directory asks iSnare for their latest articles. There is often no password entry required by the distributor.
Some might use automated software too. As thing2b mentioned it would also make sense that some of them have agreements with the article directories. Once the agreement is setup they probably have a way to send in bulk submissions as long as the distributor guarantees quality.
I use submit your article this service allows me to create several versions of the same article before they distribute it to all the different article directories. The different versions of the same article is great for avoiding google's duplicate content penalty.