Existing users without blogs

Hi Guys,
I have a directory site that has existing users that have not got blogs and was wondering what is the best way to create a new blog for each one whether their is a plugin or if I have to do it manually!

The problem I have is I created a new custom directory and custom default template so when a user fills out the registration form the details go into the template so all users details are in the same layout etc... So people see all the listings with a snippet of info and when they click on the read more link it opens up the default template showing all the details.

But since doing this all new members that signup it is working fine but I cannot seem to get my existing users to get the blog!

I have tried copying all their info and deleting them from the database and then re-registering them but still it will not create a blog for these existing users.

Could someone be so kind as to explain how the blog gets created for a user

Thanks in advance