I have a simple script that casts poison on my tamer and keeps an eye on my health. If I get to a certain threshold and the pet has not cured me, then I cure myself and reset.
I like the additional thinking about using discord on the pet. I don't know why that never dawned on me. Without discord, I believe this method caps out around 113-114. That would not be hard to add.
I have initially trained healing wearing a Cloak of Corruption or being in Lich Form. Either of these reduce your HP, but will not allow you to die. If you are concerned about karma, then 45 minutes in Wind taking out the demons and you are back at Lord/Lady. Your bonded pet will happily heal you as long as you are logged in. A non-scripted method is to hang around a popular bank where players pop in and out with your journal open - which just their names updating the journal was enough to keep you logged in. Another method was opening the New Magincia bazzaar vendor menu to remain logged in.
I have a suit with 100% LRC and self repair (or no durability on the items, like a Pendant of the Magi), so that there isn't a durability issue to content with when casting poison on myself for these training sessions.
I just looked at my script - it is kinda ugly, but shows the pet skill progress and adjusts accordingly. It doesn't cast poison on my tamer until the pet can actually have a chance to cure poison.
I have attached the routine that reads the pet values. It requires having the script kalocr.txt in the same directory as your easyuo executable. Feel free to incorporate that into your script, if you wish to post it.
The routine intentionally strips the decimal point from the value, because EUO numbers are integers.