Just trying to clarify.
Fast cannot stack with fast, slow can not stack with slow. (Page 20)
If a target has fast, and receives slow, or vice versa, the two cancel each other out. The model is not effected by either slow or fast (page 34)
In the example with Lilith (page 34) the two castings of slow are not stacking. One is cancelled making the other the only one affecting Lilith, yes?
It is my understanding that you can still cast slow or fast on a target multiple times, the effect just doesn't stack. So in the example with Perdita and the Student of Conflict, let's say he does cast fast on her. She does not become Fast (+2) because they don't stack. But if an enemy then casts Slow on her it would cancel one of the Fasts out and itself be cancelled by the Fast. This would still leave her with Fast (+1) as she had two occurrences of Fast on her before slow was cast, correct?