My 13 year old dog had a large skin tag the size of a quarter growing on her elbow. Though ugly, I didn't want to put her under the stress of anesthesia just to cut off a benign skin growth. I researched and found two methods on youtube which I used simultaneously.
First, I tied a cotton thread, wound twice as tightly as possible and then knotted off around the very base of the skin tag. Then I coated the skin tag with clear nail polish. If you go to youtube, you'll find a kindly man who has treated many dogs with these two methods (separate videos). Urls are below.
At the 3 day mark, I tied another piece of thread to ensure as the skin tag had shriveled considerably in size and you need it tight to cut off the blood supply to the skin tag. I also coated it again with clear nail polish.
It took a week before the large skin tag had completely shriveled up and turned black. I then sterilized some good scissors under a flame and then snipped the dried tag off at the base being careful not to snip her skin. She had no pain when I snipped it off and there was no blood. Also, it doesn't appear that tying a string around the skin tag caused any pain or discomfort at all. She didn't lick the skin tag once the whole week.
It can also work on other growths besides skin tags like cysts and tumors.
The videos I watched first before attempting this:
https://www.youtube.com/watch?v=56Wi5Gn6cB4 (the string method)
https://www.youtube.com/watch?v=A9uzmYJvehA (clear nail polish method)