XP Pro Sharing: adding a User for shared resource?

I'm wondering if this is one of those 'good ideas' that never worked right for microsoft on Windows XP Pro sp3.. I have a server running XP Pro that acts as big store, media machine etc for everything else: IOS, 'droids, Win7, xp, 8.1 et al. I'm trying to tighten security a tad. Simple File Sharing is "OFF" but I have a number of folders shared with "Everyone". I'm trying to ditch "Everyone" and instead enter specific users.

in the Sharing Permissions panel for each shared resource on the XP side there is a way to "check" the name of a user or resource for which you wish to grant Permission to the shared resource. But despite the fact that everything in the arsenal is alive and well on the Workgroup [can browse them, use them, log into them, etc from the XP side] the only machine that comes up in that Permissions panel is the local one [the one serving as server for everything]. If I try entering a VALID resource or user on the lan, i get nothing... the Check fails, presumably because it only is looking on the local machine, and does not acknowledge anything at all on the LAN.

is there something I need to turn on or setup, or is this just a "feature" of win XP ? Is this why everyone seem to say "look, just setup a separate user account on XP for that matches PRECISELY the login credentials for any/all other users that might want to connect" ???

and if that is the only way to do it... I wonder how to ID the droids and IOS devices? maybe that's another story. right now they work swell...

alternatively, is there any other way to tighten security so that the XP Pro system is not quite as available as it currently is?.... I can't think of a way other than managing the router etc security stuff