Start with a decision, not decoration
A useful training handbook brief names the reader, the decision or action the page should support, and the evidence required before design begins. For this project the audience is learners and trainers following a defined programme or process. The working objective is to organise explanations, activities and references into a dependable learning sequence. Write those two statements at the top of the brief and test every proposed section against them. Material that does not help the reader understand, trust or act should be removed, shortened or placed in a secondary channel.