I've doled out a lot of doses of liquid meds over time and relate wholeheartedly to your situation. Aspiration and aspiration pneumonia are horrible fears of anyone in your shoes. I doubt that any of us without professional training could give you a foolproof method, but I would love to hear how often those with professional training have the same problems getting meds into sick birds.
My techniques have always been, first, calming myself before approaching the bird, just stopping for a second or two and slowing my breathing, relaxing muscles, and telling myself I CAN do it. I approach casually, talking with the bird in a friendly way. I use as little restraint as needed for the bird and always keep him upright so gravity works for us. I insert the syringe as close as possible to where the upper and lower beaks meet and squirt a small amount at a time, allowing him to swallow it before the next squirt.
The best way IMO is to serve the meds in a tiny bit of food the bird loves and fully devours pronto. I'm lucky to have a very food-motivated amazon who is on a lifetime regimen of 3 daily meds that he eats this way, praise be

I've always cultivated a love of plain, fat-free yogurt by my flock for just this purpose of delivering meds. Each gets a little dab of yogurt daily so they don't even realize when I've spiked it

I've had several smaller birds who love the taste of their meds and will lick them from a tiny condiment spoon. Sometimes it takes a few tries for them to realize this is a special treat just for them

It's worth the effort!
Good luck to you and your lovie.