Some time later... I did go ahead and paint some of the chassis detail, etc. I enjoyed doing so, and felt it was looking ok, but... well, you'll see later!
At this point our preparations for our imminent move to a new home took precedence. I did actually do more on the model (and this post!), but the update was lost during one of the many super-crappy network coverage outage moments we suffer from in this locality.
Consequently I've lost the part where I base-coated all three components parts - 1/2-track, gun, trailer - with the matt grey car undercoat I'm using, and instead I'll end this post with the kit in her dunkelgelb dressing, as she currently stands.