Some organizations use the Jobs section for recording training since that is easy to report on for hours attended. In the Reporter volunteers are given Placements at jobs. The Jobs section has a lot of custom codes which can help you define the participation. The Impact section of Jobs works well to count up to two things when entering hours for the volunteers at that "Job," aka training.
Another way to track training is to use a custom code in the Volunteers' records with a drop-down list of the various tiers in your training program. Codes can be moved to pair with dates, text, or number fields to define any range of things.