Eigenvector wrote:
So now that I've punched holes in my walls to fix the galvanized pipes, I'm
wondering what is the most accurate way to repair the drywall.

I cut most of my holes using a punch saw, just jab it in and cut the holes,
but is it more accurate and elegant to use a knife when cleaning those
holes? Also when repairing, is smaller better, that is is the smallest hole
you can cut to clean the drywall the best or is a larger hole easier to work
with?

for small holes, cut your holes into some regular shape, like a square
or rectangle. take a scrap of drywall somewhat bigger than what you
need, and in the center of this scrap, score the rectangle you need
from the back side of the drywall. snap it, but leave the front paper
intact all around your patch, so it acts as drywall tape. helps if the
drywall is a little damp. apply this patch by mudding into the hole,
with the flaps of paper acting as your tape. not only do you not have
to monkey with wood backing, the paper lays flatter than tape so it is
quicker than mud and leaves an invisible patch. this is a slick
trick...heard it called the "california patch".

yes, and use a knife to clean up jagged edges.