You do raise a few good points. Although in the case of the former, I would assume he would have an apprentice or a similar system of learning in place. And some of these items are natural products and may be limited in quantity to preserve their sources from over-harvest. Besides, in the case of people brought here from other world, our stays here are extremely unpredictable in terms of length, anywhere from one or two months to several years. It might take a long time and very fine work to learn to make something as complex as a Pokéball that must work perfectly; time that a student might not have to learn properly, let alone put to use.