Betadine (povidone iodine) is generally considered safe.  I know several
surgeons that insist on it, and several others that don't think it does
any harm or good.  

There should always be a water wash first, before you put in Betadine or
an antibiotic ointment. For the drugs to work, they have to be in
contact with the tissue, and loose scabs and various crud get in the
way. That being said, you don't want to disturb a scab, so don't use
much water pressure -- something like a squeeze ketchup bottle would
probably be safe for someone that isn't experienced in judging healing.
Even then, it's rare to use something as high-pressure as a Water-Pik:
it's usually gravity flow from an IV bottle, or a syringe. When the
higher pressures are used, you typically want some kind of pain control.

Seriously, the most important part of wound care is keeping it clean.
For infection control, disinfectants and antibiotics on the surface
aren't remotely as effective as oral or injected antibiotics, which
isn't an option here.

Victor Martinez <me@nospam.com> had some very interesting things to
say about Re: Good News:

A while back, we were babysitting DH's parents' cat, and discovered he
had an abscess (sorry to say we didn't realize what we were dealing
with until it started draining on its own). What we did was I
restrained the cat while DH got as much of the gunk out as he could
(agh, what a smell!), then he applied hydrogen peroxide, followed by
Neosporin-type ointment. When DH's parents reclaimed the cat and took
him to his TED, we were later told TED thought we'd done quite well at
caring for the problem.

I don't know where he's living at the moment, he's visiting my neighbour
for food. We're going to let him do as he like for a couple of weeks
while he puts some weight on.