Wireless printing to unsupported printers

Okay so I have searched the internet, and maybe I am missing something, but I can't find out how to print wirelessly to unsupported printers. The guys at Apple "hinted" to me that it is possible, it's just a matter of finding out how, and following every step to a T. But of course, they can't tell me how to do it, for obvious reasons.

So can anyone refer me to a site to set this up? I have an Airport Express, and I have read about people doing it, so it's KILLING me that I can't!

Thanks in advance...

Trey