How much time do you have on a daily basis? Grab a book or some sewing and go out and just sit with them every day. No trying to touch or grab them. Sprinkle some treat around you; don't worry about it if they only eat it after you leave. Eventually put food in your lap or hold food out to them, but do not try to touch them! Maybe it will get to the point where they trust you reaching out for them and maybe it won't, but the best way to give it it's best chance is to never try it when they're sounding out how safe it is to be near you. Once some of them have formed a habit of eating out of your lap/hand, try slowly pushing a hand or finger into their feathers a bit. This should be done in such a way that it doesn't really register to them that you're reaching out to them, but more like they're leaning into you - like it was their idea. You can try pets or little finger wiggles in their feathers after they're used to that. As for actually picking them up, I only ever pick up birds that are super tame to the point that they're underfoot or flying up to my shoulders, or if they need to be doctored, and I never do it without treats because so much built up trust can be undone with that action. The tamer they are (or the more food motivated they are), the shorter the grudge over being picked up, but it's patience, time, and exposure that gets you there.
