No, that method will not work for pre-Intel Macs.
What do you see when you start the Mac? Does it show you a list of users?
Do you have a CD you can use to boot your PowerBook? Preferably the original System Restore CD that came with the PowerBook, but anything that can boot the Mac will work. Insert the disc and hold the c key while you start the Mac.
You need to boot the Mac from some other disk so that you can bypass the Login screen. Any CD that will boot OS 9 will work. Find one.
Once you boot the PowerBook from CD, you would navigate to the System Folder and locate Multiple Users Preferences file. That will eliminate the password.
I asked the Hosts to move this question to the Classic Mac OS forum, where you will probably get more assistance in locating such a disc, or perhaps finding another way around this problem. If you have another Mac, for instance, you could use FireWire Target Disk Mode to locate and delete that file using that other Mac.