Awesome, thanks! I'll try this out later. I did find out in the meantime Windows supports "old-school" networking without Homegroup, but tried another tutorial which was similar but didn't work at all.
Neither of my computers was able to find the other by name - I checked they're in the same workgroup, pinged each other successfully, tried by IP address, checked that required services are running, even firewall settings, but no go.
Maybe I'll have more luck with your guide.
In the meantime I'd still be interested to hear about any possible 3rd-party solutions that don't rely on Windows' own networking at all. (similar to FTP but more simplified)