Forster did not feature in Brazil but won his second cap in a warm-up against Honduras before picking up the knowledge of team-mates and coaches alike.
The 26-year-old linked up with the Celtic squad in Austria after a short break, as new boss Ronny Deila prepares the squad for the forthcoming Champions League qualifier with KR Reykjavik.
"It was a fantastic experience. It was great to be part of a World Cup in Brazil,” Forster told Celtic TV.
"It would have been nice to have stayed in the competition a bit longer but we played well in the games and didn't get the results we needed.
"On a personal level it was good to be involved. I think I learnt a lot. You spend a lot of time around people that you're not normally around.
"You watch and learn what other people do and try to take one or two per cent from other people and incorporate that into your game, or your training or gym work. There is plenty you can learn."
Forster is already keen to get back into action with Celtic though, with that first competitive game in Iceland taking place on July 15.
"I've only had five days or a week off," the former Newcastle keeper said. "The season finished and straight away it was all about the World Cup.
"The World Cup finished and I was thinking about getting back here for pre-season and hitting the ground running.
"It's important we are switched on and everyone gives 100 per cent through pre-season because we all know how big the Champions League games are."
I'm pretty sure anyone would have enjoyed a three-week holiday in Brazil- fictionalemu