Debtransform and distribution-specific adjustments

Hi, I'm using the "Alternative method of creating Debian packages", as described at https://en.opensuse.org/openSUSE:Build_Service_Debian_builds#An_Alternative_... (i.e. debtransform). I now have a package which needs slightly different build dependencies for different Ubuntu/Debian versions. How can I specify those? Additionally, I'd be quite interested in a way to reduce the duplication of the build dependencies, which currently are listed twice, once in the *.dsc file, and once in the debian.control file. Is there a way of doing so? Thank you! Philipp