This is a quick question. I want to level up my TM as much as I can while being afk drilling, but I'm not sure if the depth of the soil matters for that, or if it is better being at a field where I can do lots of drills (e.g Coral Beach fields). I know the type of drill matters, but I'm not sure about the depth of the soil. Also, is there any drill in-game that is the best for doing this?
Thanks in advance~