Some I have to take in, some do it themselves, and some I do myself. I have a 14 y/o who needed at least once a month for most of his life. Now he has a tumor in his anal gland and needs it every few weeks.
If you're doing it at home I recommend the external version, unless you have a helper. Most dogs aren't fond of having a finger or two in places they shouldn't be and it can get dicey without a spotter.