Medicating ferals without catching them

One of the ferals in my 'backyard' flock was showing definite signs of canker, so I tried out an idea that seems to be working:

I mix up a day's worth of metronidazole and dip a small amount of soft bread in it until it soaks it all up, and in a bowl I have soggy bread (with only water).
I throw the patient a tiny bit of soggy bread, and as the others start to arrive, lure them away by throwing lots of soggy bread. Then before the patient moves away to join the others, I throw her the medicated bread while the others are busy.
It's quite a choreography, but it's working. Today was day 3 of the treatment, and the patient is improving!

You can buy powdered metronidazole, mix 1 teaspoon per 1 pound of seed...the seed should be lightly oiled with just enough oil so that the powdered metronidazole sticks to it[this would be a tiny amount], and feed to the birds for 5 days.
But...whatever works...

Thanks, Charis!
I've only got metronidazole in tablet form at the moment, but I'll try to get hold of the powder. Generally I only medicate ferals when the bird's immune system isn't doing the job, but it seems a good idea to medicate them against canker twice a year as a precaution.
What's the strength of the powder you use, in case they sell me a stronger or weaker one?

Thanks again!

It's 20%powder.

Thank you!