As pdeeh says, there's a lot of information in the "stickys" and elsewhere in the forum.
With a little care, making a simple emulsion is not beyond the ability of most darkroom workers with a little experience and application.
But commercial emulsion formulae and modern sensitised products generally are the result of many decades of R & D, a detailed knowledge of chemistry and physics, and gradual development and improvement over many years.
Kodachrome was probably one of the most complex products and the history of its original invention is well recorded. The inventors must have had enough knowledge of sensitive materials and colour chemistry to have at least an idea of the correct processing chemicals to start their experimentation, but even then the film and the processing was redesigned and improved over probably some 50 years.
Like a lot of industrial products, Kodachrome manufacture also depended on the skills of the factory operators and emulsion makers. All the data is fully recorded in patents and other published material, but I doubt it could be replicated again without the skills and experience of the workers. (Perhaps a bit like the Apollo moon landings, apart from anything else, so few of the original designers and experienced engineers are still around now that it would be almost impossible to repeat in their original form, even if all the blueprints and information were still available.)
