The setdriver command will fail if in Samba's mind the queue is not already there. A successful installation displys the promising message that the:

Printer Driver ABC successfully installed.

following the adddriver parts of the procedure. But you may also see a disappointing message like this one: result was NT_STATUS_UNSUCCESSFUL

It is not good enough that you can see the queue in CUPS, using the lpstat -p ir85wm command. A bug in most recent versions of Samba prevents the proper update of the queue list. The recognition of newly installed CUPS printers fails unless you restart Samba or send a HUP to all smbd processes. To verify if this is the reason why Samba does not execute the setdriver command successfully, check if Samba “sees” the printer:

root# 

rpcclient transmeta -N -U'root%xxxx' -c 'enumprinters 0'|grep ir85wm

        printername:[ir85wm]

An alternate command could be this:

root# 

rpcclient transmeta -N -U'root%secret' -c 'getprinter ir85wm' 

        cmd = getprinter ir85wm
        flags:[0x800000]
        name:[\\transmeta\ir85wm]
        description:[\\transmeta\ir85wm,ir85wm,DPD]
        comment:[CUPS PostScript-Treiber for Windows NT/200x/XP]

By the way, you can use these commands, plus a few more, of course, to install drivers on remote Windows NT print servers too!