Making a trimmed copy of Yosemite

no, there is no special software to do this other than the Yosemite installer itself.

Otherwise you can refer to this document as to getting close to a factory reset mac has already been configured by a user

What to do before selling or giving away your Mac - Apple Support

As long as you downloaded it from the App Store when it was available, you should be able to use the AppleID used to download it and re-download the installer from App Store / Purchases tab.

For any Mac that came preinstalled with Yosemite, a factory reset using Internet Recovery will download/install version 10.10.5 and NOT the original version that shipped (e.g. 10.10-10.10.4).

So that I don't have to go through the install process, I have a partition on an external drive (30GB) that contains a 10.10.5 install without going through Setup. So, whenever I want to install "clean", I boot to that external drive's Recovery HD, erase the drive I want to install to and use Disk Utility / Restore to block-copy from the external to where ever. This "resets back to factory" without having to download/reinstall the OS.

Once you redownload 10.10.5 from the App Store, you can run the installer from /Applications against an external drive (30GB) and Shutdown when you get to the Setup screen. Disconnect the external drive and you have what I mentioned in the above paragraph.