How to use one automation "signal" to automate different plugins on different tracks?

The formally required, long and boring what-are-you-trying-to-accomplish part

I am trying to put together a drum practice accompaniment track for djembe, consisting of 3 dundun parts - bass drums that are normally played by 3 people. Since it is important that the accompaniment should sound as natural as possible, there are several requirements:

  1. A groove/human quantize plugin must be used (bschaffl is OK), both to enforce the right inflection pattern and to “humanize”.
  2. The humanization part must be done separately for each of the 3 tracks, because we are emulating 3 musicians.

Unfortunately bschaffl is merely a time warper: the randomization applies to times, not to individual events. So in order for the 3 tracks to be humanized independently, I must use a separate instance of bschaffl on each track. However even though the 3 emulated musicians should make slight mistakes independently, they must still play in the same groove. Therefore the 3 instances of the bschaffl plugin must all run on identical settings; only the randomization must be independent.

The actual problem

How do I achieve this? How do I control an automation parameter of 3 different instances of a plugin on 3 different tracks from a single source of truth?