Q: Any keyboard shortcut combinations available at startup?

Mac keyboard shortcuts

You can configure your startup to automatically log into your admin account and enable Fast User Switching to use all your accounts easily. Configuration can be done using the Users & Groups preferences on the admin accounts.

There is no shortcut shorter than what you do now.

You can just start typing the name; however, I think there is a bug that makes the login screen inactive and you must click on it with the mouse in order to bring it back into focus to accept typing commands.

I filed a bug report about it at least in El Capitan if not in Yosemite, but I don't know if it will ever be fixed.