A guess, or could this work...
Have you tried to unzip either the Canon rpm or deb tar.gz printer driver file to convert either of them for Slackware, then returning them to tar.gz? Alternatively, would there be anything in these rpm or deb files in any variant that would help you?
I mention this because I installed my Canon MG5450 on openSUSE 12.2 from the tar.gz rpm file according to the linux guide I found on the Canon Support site. As the tar.gz file was unzipped the RPM was installed, there appeared a dialogue for installing the MG5450 as a wireless printer and that did the job.
My thought was that you could either use the same configuration function, installing from a modified tar.gz file or at least gain some information about what is going on when the dialogue configures the printer.
Have you seen this?