While Danny Lennon's side lifted the Renfrewshire Cup with a 1-0 win over local rivals Morton, the Buddies U20 team saw off Rutherglen Glencairn to claim victory.
Lennon could hand a number of his young Saints stars a jersey when they face Irn-Bru First Division side Dumbarton tonight.
And head of youth development Longwell admits he has is delighted with the progress of his Buddies kids as they continue on the road to potential first-team stardom.
He said: "It was a hard game [on Sunday] but it was also great experience for the boys.
"There was some good stuff in our play but that being said we also know that there is a lot to work on before the start of the new season.
"We had a lot of U17 boys playing in the game – six in total – so this was a very young group.
"Well done to John McGinn and Jack Smith who both shared the player of the tournament award.
"It was a big positive for them and they both deserved it.
"Over the weekend the boys showed great attitude and spirit and we'll look to carry that forward into the new season when it gets going."
Tonight's Sons clash will give Lennon the chance to see many of his fringe players in action as the new SPL season draws ever closer.
The Saints will head south later this week to face Carlisle United on Friday night before they take on Accrington Stanley 48 hours later, with the English trip set to be their final pre-season action of the summer.
Kenny McLean may be forced to stay at home, though, as Lennon sweats over the fitness of the midfielder after a knee knock as well as defensive duo Graham Carey and Marc McAusland.
Lennon said: "We didn't want Kenny coming down to Cappielow and sitting in the stand but we got a good call from him.
"He asked the medical team on Saturday morning if he could come down because he was feeling a lot better.
"But we kept him away, so hopefully, fingers crossed, there is nothing showing up on the scan.
"I think he got more of a fright than anything else.
"But whether he'll be able to travel with us next week, I don't know.
"With Graham, he's just got a tight hamstring so leaving him out was more precautionary than anything else.
"Marc McAusland was complaining of a tight calf on Friday, so that's why we only gave him 45 minutes."