Services for defence personnel or immigrants to Kapooka and/or RAAF Base Wagga, perhaps?
There were no such services to Kapooka or to Wagga RAAF Base "Forest Hill"
The only service that stopped at Forest Hill was the train to and from Tumbarumba and some small goods trains also serviced the line
Kapooka was serviced by mainline trains and passing on the loop! There may have been a railmotor passenger service for school children most likely from 1900 up until late 1940s to early 1950s! At that time schools were widely available in very small towns and farming regions which really explains why on earth is that station built there these were pretty much started to close from late 1950s until late 1970s that's why we have a lot of closed and disused railway lines people simply founded other transport options which is sad
The school at Kapooka was closed and demolished which is now located under a few houses in the suburb itself today and of course a new school was built to keep the new residence happy!
As for Wagga Wagga Showgrounds railway station! It was also serviced by a railmotor service, the showgrounds back then would have been a lot more fun which would have been opened every school holiday and weekend during that time no road entry was available which is why the showgrounds had a railway station for it's only entry and exit
Today, the only main event at the showgrounds is obviously the Wagga Wagga show in July, a few horse and dog racing and a few events including the Wagga Wagga model train and hobby expo! Overall in my personal opinion the Wagga Wagga showgrounds should be completely closed there's really no point in keeping the poor place open anymore it's embarrassing to even visit the grounds it just looks sad!! The owner just loves the money coming into the door that's all he cares about obviously being a millionair is all he cares about is money too much greed - I rather see that big massive oval in North Wagga being used as the showgrounds and other events it's more welcoming but of course the owner of that would get greedy over money too but at least it's a welcoming place to visit and lots of parking space that Wagga Wagga showgrounds just hasn't got available on a good day!
As for any trains from Wagga Wagga to Sydney! The short answer is no such service was available
There was however a service called "Riverina Express" which was short lived this went all the way to Albury and returned to Sydney the following day I believe! However, it never stopped at Kapooka only some day's it had to use the passing loop to allow bypassing passenger and freight trains!
Yes, you wouldn't believe Wagga Wagga station used to always have passengers and a completely full platform and booking office!!!