1/2 ml is not enough to gag them if done properly. Just open the beak with one hand, syringe in the other and squirt it in the front under the tongue on the bottom mandible. (beak) It will drizzle down the right pipe. Don't shoot it in fast, just a medium squirt. You can squirt up to 1ml without too much worry of gagging the bird. Any more and you can get it in their lungs. 1/2 ml is a very tiny amount.
It is always best to dose the drug as it is designed. In this case this is an oral drug. The problem with putting medications in the water that are not designed to be there, is that many drugs may not dissolve correctly, you may not be dosing them properly or some birds may drink too much and others not enough. Wazine is a bit different in that it is pretty mundane on the bird and can be served up for up to 3 days for those birds that may not have drank enough. Wazine doesn't kill anything, but paralyzes live worms. It is designed for water. You can't really over dose birds on this stuff if used properly. Safeguard is safe to use if given in the proper amounts to each bird.
Worms are nothing to mess around with. I would guess that 85% or more of all slow, sour and impacted crops in our emergency section are caused from worm impactions. Most of these birds end up dying because they are treated for crop issues when in fact the intestines have become so impacted with worms that they rupture, or the bird dies from food poisoning or because they can't defecate. Some birds starve to death long before this point as well.
So long story short, LOL, use it as directed. If you have a huge flock, just dose each one while in the coop and put the bird out after the dosage, that way you know you got them all.
hugs. Pup problems....
e I'm so excited I'd better be careful or I might pee myself 
That of course works all too well lol.
