I've updated the system with a couple more ways to earn TP, since obviously training grounds aren't magic, and you can't just pull them out of your pocket wherever you go. So, you now gain TP whenever you enter into a fight or spar, regardless of where it takes place. Also, wandering/missing-nin gain TP for whatever they write outside of major villages, since they don't have any training grounds to gain TP in. This includes Shounin.
In both of the above cases, TP gained is a 1:1 ratio for words typed to Training Points