For low-risk things, we defer assessing effectiveness to the management review (asking "were there any issues that arose because training wasn't effective?"). For high-risk things (i.e., harm could be a result if training is ineffective),
@malasuerte suggested one way (although 100 times may be excessive). You can also use an approach like "train the trainer." Other measures (for lower risk) can include quizzes or even discussion. You have the ability here to be creative so don't get hung up on a single approach. Lay out your risk-based approach and apply it.