This is an excellent guide !
It is so unfortunate, that at this point, many options are not very easy for beginners that may not have a foundation in network technologies and protocols. A cheap external NAS box may be a better alternative, but will still require some knowledge of which protocols to use for each client OS and what to activate on the NAS.
If I get time, I will work on a "pre-configured" Virtual BOX image of NT server or Windows 2000 Server since they include strong support for Macintosh clients by supporting the Apple File Protocol (AFP) as a native networking protocol choice. Thus, it will be extremely easy to create shares in the Virtual machine and connect to the machine with OS9 or early versions of OSX.
The only caveat, is that the free Virtual box network card should be configured to "bridged" (this will basically put the virtual machine on the same IP scheme as your router and give you access to all items on your physical network). As an added bonus, if the machine itself has dual NIC cards (Like a Mac Pro) you can use one NIC for the Mac Pro and configure Virtual box to use the other; I cannot tell you how much faster the Network stacks operate in this configuration. My Win7 Pro Virtual box machine attaches to 2 separate servers and is as fast as real PCs on my work network, of course I can also print to all IP network printers.
Sorry for those not savvy in networking, I think Virtual box may be a better alternative for modern macs since you can download a "pre-made" image with a working older OS that already has the bells and whistles built in