yes, it's true.Even if you have 2 whistles, a fast trainer should gain at least 4% with 18%.
The first step is to detect a fast trainer
the second is to confirm it
as about developing, there are other threads with more details for that
here Toxcatl gathered some
https://forum.topeleven.com/tutorial...ost-found.html
also I (and others) have some notes here
https://forum.topeleven.com/tutorial...-training.html