What can I do to get login page upon opening a new browser instance, when I'm already logged onto same site as another user.

I want to be able to quickly see the effects of changes I make as admin user, by opening a new browser and hoping to log in as anonymous user or another authenticated user. However, when I start a new browser instance and enter the site URL, while still logged in as admin user on the already existing browser instance, the site front page shows up with the admin user's Navigation menu and no login authentication fields.

What can I do to get the login fields to display upon every visit to the site on a new browser instance regardless of any existing browser sessions?

Thanks in advance.