Adding the vacuum pipes to a carriage is something I have to psyche myself up for.
It's not that it's an especially tricky or boring job but it does involve bonding metal to plastic with super glue which is never the most satisfying of jobs.
On the Disco Car it's twice as bad because these push-pull vehicles had two sets of brake pipes - one for running as a normal train and the other was also required to operate in push-pull mode.
I don't really feel qualified to explain it so if you'd like to know more I'll refer you to this Festipedia page.
Anyway, all that really matters is that it looks good, eh?