Here is the troublesome passage:
ὅσοι δὲ τοῖς νεωτέροις εἰσηγοῦνται μὴ δι᾽ ὧν τὴν δεινότητα τὴν ἐν τοῖς λόγοις ἀσκήσουσιν, ἀλλ᾽ ὅπως τὰ τῶν τρόπων ἤθη σπουδαῖοι πεφυκέναι δόξουσι, τοσούτῳ μᾶλλον ἐκείνων τοὺς ἀκούοντας ὠφελοῦσιν, ὅσον οἱ μὲν ἐπὶ λόγον παρακαλοῦσιν, οἱ δὲ τὸν τρόπον αὐτῶν ἐπανορθοῦσι.
Below is my translationese, phrase by phrase. There is a lot of guesswork in my translationese.
ὅσοι δὲ τοῖς νεωτέροις εἰσηγοῦνται [those who instruct the young]
μὴ δι᾽ ὧν τὴν δεινότητα τὴν ἐν τοῖς λόγοις ἀσκήσουσιν,
[not by means of-what-things they will learn cleverness in speaking]
ἀλλ᾽ ὅπως τὰ τῶν τρόπων ἤθη σπουδαῖοι πεφυκέναι δόξουσι,
[but by what manner of means they will be thought by-nature-to-be men of good character]
τοσούτῳ μᾶλλον ἐκείνων [by so much more than the former]
τοὺς ἀκούοντας ὠφελοῦσιν, [the hearers they help]
ὅσον οἱ μὲν ἐπὶ λόγον παρακαλοῦσιν,
[(for) the former encourage (improved) speech]
οἱ δὲ τὸν τρόπον αὐτῶν ἐπανορθοῦσι.
[but the latter correct their ways/behavior/conduct]
I don´t understand how the former/latter distinction works in the Greek in this passage.