I find the small items placed in amongst the food and slowly built up and increased in difficulty over time does not overwhelm them, they learn to forage without any fear or stress and start to enjoy working for their food.
I taught my macaw to forage without any interference from me like that as he was growing up, I would place small round wooden beads and them plastic dummy (binkie?) toys in with the food and each day add a couple more items or I would make paper stars to throw in the food dish till they literally had to be moved for him to see and get to his food.
You want to start with really easy things (cut up lengths of straw, beads, screwed up paper etc) and when your bird gets the idea you can start to do things like cover the food dish with a sheet of paper tied in place and put a decent size hole for your bird to start ripping away at, each day you make the hole smaller till there is no hole.
I found teaching foraging this way was really easy as they know the food dish has food and as long as they can still see the food and are not scared by what you put in the dish then they will usually work at getting to it as long as the challenge is fairly easy and as the skills grow so does the level of challenge you give them. Once they have mastered this stuff you can start to introduce putting foods into toys, small boxes or tubes, wrapped in paper envelopes etc. then eventually harder forage toys.
