Printing the most dense possible black

Hi,

Is there a method from photoshop that will let me put the most ink down on transparency film.

I am printing film positives for screen printing, and unfortunately i dont own a post script printer (have a canon pixma mp540, so i cant use a rip).

Someone on another forum was saying something about setting the CMYK seetings to 100C 100M 100Y 100K to produce darker blacks on the film. They said this was a photoshop/corel setting and could be done on any inkjet printer. They neglected to explain how to do this though, as in what settings in photoshop, file type, etc.

Does anyone have a clue what they may have meant, or any other tips please would be appreciated.