Worked in past with vocational students and they expect to learn by doing which is not wrong, so it seems that practical should be prioritized and theory is used as review (here and there); however, safety and environment hazards are always addressed first. The best ratio may not be the same for carpenter, welder, etc. Prior to deciding ratio, I'd create a chart:
What is the main goal or outcome that I'm trying to achieve?
What are the learning objectives under this outcome?
How can we achieve them (strategies) and how can they demonstrate achieving them (assessment, project, etc.) ?
For each objective, what are the competencies and necessary skills (reading, writing, teamwork, numeracy, etc.)?
In the strategies, consider their learning style and previous experience or knowledge. Having them generate a document such as a standard operating procedure for an objective(s) can show their understanding of a process and how to carry it.