Automatically update the closing tag when open tag changes with Sublime Text 2 on Mac OS X

See the `H2` tags? How can I change them all to `p` tags without manually going from line to line. `cmd+d` is not viable because of the varying lengths of the inner content. I found something called Emmet Plugin which I installed but can't get it to work. (Followed steps and confused by docs http://docs.emmet.io/actions/go-to-pair/). Thanks for the help. --UPDATE-- Not using a regex. Just to clarify I want something that will automatically update the `closing tag` if I change the `open tag`.