Have you considered using a virtual machine as your training environment? You could use either the free Microsoft virtual PC or VMWare Workstation. The VM can then be reset to a previous snapshot without any overhead in terms of machine rebuilding and this solution is used extensively in some of the training and demonstration environments I have seen in operation.
If there is a specific reason for actually reimaging the entire hard disk, or at least a partition of the hard disk, I would strongly recommend using an external USB hard disk rather than a USB flash drive, due to the much greater performance of the external hard drive. I have used the small pocket 2.5 inch external drives as technician rebuild tools, using a WinPE boot and an hta file to provide a basic GUI for the techs to select a build, etc.
You can use the basic Ghost files with WinPE or use the native imagex utility that comes with WinPE and is free. If your laptop has sufficient disk space you could put the image on a second partition and just have the machine dual booting.
My article here: https://www-secure.symantec.com/connect/articles/readyadventures-winpe describes how I did this using the version of WinPE that comes with Ghost, albeit building it from scratch using the Microsoft download (free). There is also a link to an updated article that uses WinPE V3 which is compatible with Win 7 drivers. It all depends on how much time and technical expertise you have.
If you want an "off the shelf" solution that is up to date, check out Paragon Partition Manager.