How to level TM:
* For Senses all they really have to do is drill, and find an item.
* But more often, just training is much more efficient and faster than just drilling which you either like... or don't like.
* Since you are level 20, you can carry on to the next chapter of Episode 0. If you haven't don't the Don Giuvanni section, then do it, and then proceed to the "Friendship Stone" (or whatever) section.
With all that done it should get your TM to about 23. And then you can just grind it out k?