You can train them when they are adults but it takes a little more effort. Peanuts and safflower are great treats to lure them to your hands. You'll want to put it in with their food first so they get the taste. Raw, shelled peanuts, by the way - Spanish are the best since they are smaller and more bite-sized for pidgies
Feed your birds twice a day (they only need a couple tablespoons per bird each time - or you can leave the food in there for a 10-20 minute all-you-can-eat buffet and then take the food out when the time is up) so you can control when they are hungry. Before you feed them each day, offer it in your hands first. I sit on the floor of my loft with my legs indian-style, fill my hands with food, and sit them on the floor in front of my legs (cause if you sit there holding them out, your arms will get tired, LOL). I may spill a little on the floor near my hand so they are more tempted to get close. Soon they will be comfortable with coming up and eating from your hands and they will associate you with food time. If they don't come around at first, that's okay - just dump the food in their tray/feeder, and stand back while they eat. If you are there when they eat, it helps them get used to you and learn that you aren't dangerous. If they are still too nervous the first time to even come down and eat while you're in the loft or near the cage, you can just back away and they should give in to hunger. Once mine are used to eating their normal food from my hands, then I can sit in there and feed them a treat after they are done eating their typical food. It's like us and icecream or a favorite dessert - they'll make room for peanuts if they have to
I can also throw a few peanuts across the floor so more than a few birds can get a treat at a time (only so many can occupy your hands at one time, afterall)....and they'll chase them to get the peanut first
Like chickens and their treats. It's hilarious and cute