As others would agree, reaching out well before would be ideal. It takes time to build relationships, but if you're reaching out to a bunch of journalists, here are some tips:

- Make a Twitter list with all of the contacts on your media list where you can skim the feed once or twice per day. Engage with these journalists- retweet their content, leave a reply, answer any questions they ask, etc. The more often you engage with them, the more likely your name is to stick out when you reach out and pitch them! Here is a GREAT article about building relationships with journalists with a 6-week plan: http://spinsucks.com/communication/media-relations-done-well/
- Be sure to craft a compelling pitch to accompany your press release- it should be a teaser of the release so the journalist can decide whether or not they want to read more.
- It's also a great idea to craft another pitch and press release for the day you launch. At that point, anyone who has written about your project will have the chance to update their readers.

I hope this helps, and best of luck with your campaign!