In versions past 3.xx (available for a while) simply editing the shortcut's command line to include --enable-user-scripts on the end, instead of utilising GreaseMetal, will allow you to install scripts from userscripts.org, the largest repository of scripts on the web.
there you will find many scripts that work with chrome, including an adblock+ style blocker, which used with another, discontinued but still good, called Adsweep (from Adsweep.org) should cater to your adblocking needs.
So. To recap: rightclick the shortcut for Chrome, you'll see a [target] box with something like C:*USER_PATH*\Appdata\Local\Google\Application\chrome.exe. Add "--enable-user-scripts" sans quotes. Save.
You'll then have to create a "User Scripts" directory in C:*USER_PATH*\AppData\Local\Google\Chrome\User Data\Default\ and save the .user.js files you've downloaded in there and Bob's your immediate relative.
Long-winded answer for an overly long-winded process, I know. But it's the route that's worked best for me :)