Ankh-Morpork Guard
First Post
I don't know of anything saying you CAN'T. Only requirements would be that if you either have ranks in the skill, or it can be used Untrained.
Also, pretty much EVERYONE could use a Heal Another use. But note that only Aerek is in double digits with his VP. The rest of you are pretty much on the bring of exhaustion. Because of this, Barrick, you can only use Heal Another a few times depending on the result of the skill check.