I've found for day-time docking works best by letting them roam in an empty room (or maybe a sectioned off area). They know somethings up and won't like it but if they have a bit of freedom and can explore, they will be a bit happier. Don't forget the basking light. You might want to try night-time docking though, especially if you think the injury is minor and not bleeding.
My suggestion, take the turtle out of the tank and use a towel to dry him down. You can do the betadine then (half with water is OK... but the stuff can cause stains to be careful). Let that dry then polysporin.
If you looking for a vet in the GTA, you might want to shoot an email to
http://littleresq.net/ as they should know who to go to.