What is the correct way to move or remove content from DotNetNuke and inform Google and the other search engines that it no longer exists at the old location?

I was looking thru the list of pages that were index by Google and discovered that Google still had them in the index.  When you click in the link DNN takes you to the home pages since the linked URL doesn't exist. It seems to take several months for Google to drop these pages. Often I add them to robots.txt or go to Google's webmaster tools and explicitly request the page to be dropped from the index. 

All this is manual, time consuming and error prone. Is there a better way to do this that works with multiple search engines?  I assume that if a 404 was returned Google might act a little quicker, but don't know.