In both of the Presbyterian or Reformed churches I've been part of as an adult, the leadership liked to say that those selected to take the officer training courses were, in many ways, already doing the work of an elder or deacon. They had already shown themselves to likely be fit for the office by their wisdom, godliness, devotional life, character, and by the fact they were helpful to others in the church and eager to join in the church's work.
So the training did not need to teach these godly qualities, which are hard to teach anyway in a short period of time. The training mostly had to make sure the candidates were familiar with the confessions and in agreement, understood church polity and the local church's approach to ministry, and got some specific training on good practices for elders and deacons so that common mistakes could be avoided.
When I trained as a PCA deacon, the "good practices" part of this included reading the old Resources for Deacons book compiled, interestingly, by Tim Keller back when he served in that capacity for the denomination. It was dry, but a useful resource.