Even simpler now, you can tap the icon (letter or picture) to the left of as many emails as you want, then tap delete to remove them.
Alternatively, you could try the new Inbox app by google and mark emails as done which sort of archives them outside of your inbox. I prefer the new inbox app as I like to keep my inbox clean.
If you install it and need an invite send me a private message, I have several invites available.