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はたから見て、俗な言い方をすれば、自分は、淫売婦に依って女の修行をして、しかも、最近めっきり腕をあげ、女の修行は、淫売婦に依るのが一ばん厳しく、またそれだけに効果のあがるものだそうで、既に自分には、あの、「女達者」という匂いがつきまとい、女性は、（淫売婦に限らず）本能に依ってそれを嗅ぎ当て寄り添って来る、そのような、卑猥で不名誉な雰囲気を、「おまけの附録」としてもらって、そうしてそのほうが、自分の休養などよりも、ひどく目立ってしまっているらしいのでした。

I am confused about the parts marked in the bold.

...淫売婦に依って女の修行をして ...

Can I translate 「女の修行」as 'learning about women' ?

... 淫売婦に依るのが一ばん厳しく、またそれだけに効果のあがるものだそうで ...

What does「依る」signify here ? I understood this as 'according' (to the prostitutes)

Would the above be a close to correct translation of the block of Japanese text ?

My translation for the above sentence
If you look closely, to put it in layman terms, the prostitutes thought I was learning about women. On top of that, I got remarkably good recently. According to the prostitutes, learning about women from prostitutes is a really difficult thing in itself but getting good only through that was quite something. Soon, I was getting followed by women. As if by instinct (not limited to prostitutes), women would sniff me out and try to get close to me. That kind of indecent and shameful atmosphere was so called "service" from them. It was more of an eyesore than a break to get away from it all.

Thank you :)

"Learning about woman" is not far but sounds a little too indirect to me. In this context 女の修行 directly refers to learning how to sleep with women. ～に依って is "relying/based on ～", and here it signifies his knowledge and experience about women is based on prostitutes. はたから見て is "seen from outside" or "from the standpoint of others".

The basic structure of this long sentence is like this. Keep in mind that 自分 (progagonist) is the topic of the whole sentence, and らしいのでした relates to almost everything before it in this sentence.

はたから見て、俗な言い方をすれば、

Seen from the outside and put in a slangy way,

自分は

as for myself:

1. 淫売婦に依って女の修行をして、
   
   (I) learned how to sleep with women using/relying on prostitutes,


2. しかも、最近めっきり腕をあげ、
   
   (I) even got remarkably good (about women) recently,


3. 既に自分には、あの、「女達者」という匂いがつきまとい、
   
   (I) already got that aura of "playboy" sticking to me,


4. 女性は、（淫売婦に限らず）本能に依ってそれを嗅ぎ当て寄り添って来る、そのような、卑猥で不名誉な雰囲気を、「おまけの附録」としてもらって、
   
   (I), as an "extra bonus", gained the lewd and dishonorable atmosphere that makes women (not limited to prostitutes) sniff me and try to get close to me by instinct,


5. そうしてそのほうが、自分の休養などよりも、ひどく目立ってしまっている
   
   and this (rumor) ended up being better known than my recuperation itself

らしいのでした。

...seemed to be the case.

And "女の修行は、淫売婦に依るのが一ばん厳しく、またそれだけに効果のあがるものだそうで" is a parenthetical aside, i.e., you can read this part as if it were in parentheses. It means "—learning how to sleep with women is said to be the hardest but thus the most efficient if you rely on prostitutes—".

Also note that these "aura of playboy" and such are not something the protagonist was aware of. Everything between 自分は and らしい (1-5) is what others are rumoring about him. He was unaware of such a reputation, and that's why he said 堀木にそれを指摘せられいやな気が致しました.