prevu is a useful tool for building packages from different releases.

However, when prevu fails (due to changes in the .dsc format, or depending on options in dpkg that were added in a specific version), remember prevu is just a script for setting up a chroot build environment, and you can still grab the orig source and ubuntu/debian diff, apply one to the other, then use dpkg-buildpackage to do the same thing. It won't be quite as neat, as you will need to install the build dependencies, but it should work where prevu doesn't.