Day one: the queue, not the product
Teach how work arrives, what the statuses mean, who owns what and how to escalate. An agent who understands the process can hold a conversation while still learning the product. The reverse is not true.
Day two: read, do not reply
Have them read fifty resolved tickets in their department. Nothing teaches tone, vocabulary and the shape of common problems faster, and it costs nobody any time.
Days three and four: reply under review
Draft replies that a senior agent approves before sending. Feedback is specific and immediate, and the customer never sees a learning experience.
Day five: the easy categories, unsupervised
Give them the two or three categories your knowledge base covers well. Confidence comes from resolving things, and these are the ones that can be resolved.
Week two onwards: QA, not supervision
Move to sampling a few of their tickets against the rubric. It scales, it produces better coaching than watching, and it applies equally to everybody rather than singling out the new person.
What shortens this most
An internal knowledge base. Teams with one onboard agents in roughly half the time, because the answer to “what do I do about this?” is a search rather than an interruption.