[azaras]

1. Is there a practical way to administer democratic worker ownership, without centralized control?

Yes, worker cooperatives.

Example: https://en.wikipedia.org/wiki/Mondragon_Corporation

2. Is it also possible to do this on smaller scales than entire countries?

Yes, worker cooperatives.

Example: https://en.wikipedia.org/wiki/List_of_worker_cooperatives

[omginternets]

Worker cooperatives are exactly centralized control. The fact that they are democratically run is orthogonal. There is still a (logically) central body with the authority to set policy.

[xupybd]

Well, I'll be. I'd love to see more of this sort of thing.

Thank you for pointing this out.

[hernantz]

And worker cooperatives are totally compatible with a capitalist society, only they shall compete with traditional companies