Myself, when I train with herbs and do something else at same time, it is currently my main source of stupid deadly errors.
I just find a sample nice trick to do a quick herb training totally safe and quick for real time: It's cutting wood with a hatchet in wilderness woods as you train with herbs. Before to do the training session you just need:
- A hatchet and probably the bridge skill plus the bridge manual.
- Take plenty morgia to train TO and WI. How many depends on your current maximums and potential maximums, plus take a few more if you do few errors. Number is 62 - (Current TO+Current potential TO)*2 + 54 - (Current WI+Current potential WI)*2 + 10/20 more for being safer. Blessed morgia are better and faster but uncursed too should do the work and still fast with this method.
- Take many mareilon to train DX. Number is 60 - (Current DX+Current potential DX)*2 + 10 + 10/20 more for being safer. Blessed mareilon are better and faster but uncursed too should do the work and still fast with this method. But don't use cursed mareilon.
- Take some devil's rose herbs to get sickness. All type should to the job fine, around 20 unblessed should be more than enough.
- If you don't have the cure disease spell, takes also some blessed curaria mancox to cure sickness.
Now exit from CoC, and go to nearest wilderness wood, eventually plan this at your next exit from CoC like to do the pyramid quest or the Griff quest.
There train TO and WI with herbs as explained in the guidebook. And cut trees. With blessed herbs and stats not too high you get the herb training after one or two tree cutting. Train them to 25 then do the same with DX and train it to 25 too. Now it's time to use sickness. So eat one devil's rose and train TO and WI to 25 with sickness, DX to 24 wit sickness. Sometimes eat one more devil's rose to be sure to keep sickness. Once DX is at 24 then use 10 mareilon in a row. Either you feel safe leaving the safe woods then it's time to exit and continue your journey, keep sickness until DX reach 27 with it or 25 or higher but the time is too long. Wait this during some more wood cutting can be nice too if you want it safer at price of more game time and turns.
Take care that carry too heavy load can break your DX training so either use the atlas spell to avoid this or be sure to use the hatchet on a square with no tree, this will allow you to use logs cut. You'll need for that the bridge skill and the bridge manual.
I noticed that, unlike mentioned in the guidebook, I could have both training from morgia and mareilon at same time. But I didn't test it a lot it was more consequences of some errors. I'll try that with my next character with same method that makes testing herb training quite easy.
EDIT: This method is only for newbies because you'll lost game time and game turns because during all this training you could do something else required and train with herbs at same time.