To prepare an herb, use a spell or the skill, prepare herbs. Note, I now consider the skill Herb Lore to include the skill, prepare herbs, even though it does make sense someone might be a knowledgable herbologist and not a healer/herb preparer at all...just not in my game, unless a PC wanted to for some reason to do with character (the Sage who knows much but can do very little).
Horticulture is knowledge of
how to grow things, flora lore is knowledge of plant life(by area/culture), something an Herbalist would likely know.
There are secveral fashions/methods in which an herb can be prepared. If you have HANDS OF THE HEALER, these ways are covered in wonderful detail...how to make a tincture, a salve, a compress of herbs, etc. Depending on what process is being used (there is one process that leaches the essence from herbs to form a concentrated paste with solvents or alcohol, so failure here would likely destroy a dose or two), how many doses are wasted would vary, depending on type of failure/partial success/etc. If the PC has 12 doses of herbs and gets 70%, the only 8 doses are gained from the initial 12. I would recommend using the MM Table instead of the Static Mnv Table for resolving this skill.
An instant Herbal cure would effectively work the same as a successful skill check, or Absolute Success if you prefer.
I play the Herb Lore spell that way. But only success, not absolute success.
When foraging for herbs, there are several methods. First, note the climates the PC are familiar with. In my game, all herbs outside those climates are at -30 on foraging and herb lore checks, above normal difficulty rating. After noting all herbs that could be found in the area, I mak a skill check for foraging using the highest skill in the group with a +2 for each additional searcher. A search takes 4 hours. Areas that are well foraged already suffer a -30 or higher penalty (or a little lower, down to 0, if not foraged recently). Remember that many locals know of the value of herbs and would be on the lookout for common healing herbs (any herb IMO light mnv or lower to find). I then take the total skill and start subtracting difficulty mods...-10...-20...-30...etc, until I get below 100, when no more herbs are found.
Another involves the MM Table, but a bit more paperwork, and honestly, it's bed time so I aint typing it
lynn