Food.
Chickens put a lot of stock in food. If you don't give any treats unless they're being social with you, you'll go a long ways.
Another trick I use is I don't give treats to get my chickens to let me catch them. That just made them suspicious of the treats.
I only give the treat after. I went through 12 days of having to shove a syringe down a chickens throat twice a day and about midway through I had a real problem. I couldn't catch her! They were getting clever enough they kept one eye peeled on me like I was a predator.
So I had the same problem you do.
I asked a friend, he deals with people who are kind of difficult, and he reminded me that the last impression is the big one. Not the first. So I no longer try to catch them with treats .. and I spend a few minutes after every bath or med dosing patting their side, talking to them and feeding a few bites of something they l.o.v.e.. They're much easier to catch now and seem a lot less stressed. Bird brains lol