I use Liquid Nitrogen, I have only done ears, and ribs.
I use a heavy brass "iron", from L & H.
I shave hair, use 99% alchohol. 15 to 20 secs does a fine job on any dog.Dog hide is thin, and easy to "burn".
I have held some longer thinking I should, and had "poor" results. I'll also look and see if I can find some nice pics.
The info posted so far, is more info than I ever got,and better than I can share with anyone,I learned by "trial and screw up". Duane