Is freezing dog skin tags or warts at home safe and effective?

Unfortunately, this is not likely to be something that you can do at home - cryosrugery is occasionally used for lesions like this in dogs, but this is not something that most general practitioners would have the necessary equipment to do. Over-the-counter products for human warts (like Dr. Scholl's "Freeze Off") are not approved for use on dogs, and would not be expected to be effective on sebaceous adenomas because these are quite different from warts at the cellular level - it's more likely that they would become irritated and inflamed by the treatment, rather than being successfully frozen off.

I have never seen any other successful option for these growths apart from surgical removal as needed, unfortunately. If the growths are quite small, it may be possible to remove them with a local anesthetic and possibly a bit of light sedation - you could certainly talk with your vet about this option if you are concerned about costs, or risks of anesthesia.