do unions help to get junior workers up to fighting shape

Trade unions will have apprenticeship programs run by the union for new members to have auxiliary classes while they learn on the job. As well as journeyman addition courses for already trained people to learn specialized skills.

Factory unions it depends on how complicated the task is. If it's a bakery, or a machine shop, then the union will probably have a class on how to work each station, or it will be part of the union deal with the factory that the employer will provide training. But some jobs just aren't to complicated. You don't need a ton of training to work an industrial bakery, just a half day on how to use the mixer, a few hours on how the ovens work safety, and a day on how each of the process lines function and you're good to go.