Your trainees are in the classroom, then they are released back to their jobs.
Their behaviour is unlikely to change solely as a result of their time in the classroom, so how much more time is required to create real and lasting behaviour change to provide tangible impact from the training course?
If you require one day in the classroom, never consider or market the course as a one day training. Consistently talk about it as a 3 day programme, one day of which happens in the classroom, and the rest spread over two months. You add your own numbers 🙂
Usually, trainees need to spend more time after the classroom than they spent in the classroom. Without ring-fenced time for experiments and practice within the normal workflow, it is unlikely that much of the material covered in the classroom will survive.
If the new learning is simple and immediately implementable, and people can see an immediate benefit, the learning transfer will probably happen. However, if something is that simple, maybe a workshop was not necessary?
A workshop would be indicated where there are complex ideas to understand and discuss, so workshop follow-up will inevitably be complex and require significant time.
Those follow up activities, spread over the duration of the whole programme, make up a learning workflow.
My best wishes, Paul