You could always download the WebKit Nightlies. This just makes it easier.
These installs are also signed by Apple, as opposed to the nightlies. What that means for the end user is that things that they expect to work, like iCloud syncing for example, will continue to work while using the technology preview. They would not work if running the nightlies. Updates to the technology preview will also come every 2 weeks via the App Store, so the user doesn't have to remember to download new technology preview builds.