"debuild -b" does a bit more, it also checks for build-depends using dpkg-checkbuilddeps. Just install devscripts package to have all tools mentioned. That's the shortcut way for what you did manually. So of course your commands are correct too. Using apt-get source -b is certainly the most easy way when you just want to recompile things. I don't get why it was not available for you. If you want to do some more testing i suggest:
To test that xbmc auto/glsl is broken, only arb works. The comments in the scripts should be executed as root, the script itself as user. Maybe somebody wants to add a bugzilla entry, i wont do that. The bug is present in ALL fglrx releases i tested so far...