That's not really necessary in any way unless you're going for the 100 title trophy and there's always going to be artes that the AI will flat-out never use unless you force them to. (Primarily the A-Artes for Cheria and Malik)
The best way to get those is to simply control the other characters.
In fact, Hubert took me the longest to get his 100 titles because the AI was too diverse on his attacks, so he had no problem getting most his adept titles his own, but had he had like no master titles until I started using him.
That said you could always just do that while progressing the story no need to mindlessly grind for that.
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