To have many blogs in blogger.com you don't need to resign up any more, with other word you can have many blogs in the same/one dashboard. The advantage of having many blogs in one dashboard is not bothering ourselves in managing them, just imagine if you have 20 blogs and each has their own dashboard, it's mean you have to sign in every time you want to make some customizations.
The steps of creating many blogs in one dashboards:
1. Go to your blogger account
2. In first page after signing in, just use "New blog" button to start creating a new blog
3. Last step; fill all required data
4. You are done...