I heard there is a trick you can to do with breeding a Ditto holding an..

Well, to be honest, I cannot really tell you whether it is true or not. I cannot give you a straight answer, because admittedly, I don't know. But I do know that an everstone should not affect what nature that your baby Pokemon will get. All the everstone does is stop a Pokemon from evolving. Thats why it's called EVERstone, they stay in that form for as long as the stone is being held by the Pokemon.

Still, I am not someone who works with the Pokemon games so I cannot tell you what crazy ideas that the Pokemon Company put into the game. Still, there is no harm in you trying that so called 'trick' is there?

Hope this helps.

Yes from the numbers I have read in the past (which are admittedly up for debate) there is a 50% chance that when you mate a ditto holding an everstone with a Pokemon that the Pokemon which hatches out of the egg will have the same nature as the ditto. Whether or not it is actually 50% is iffy, but it is for sure a much higher chance then random. So it pays to have a few dittos with various useful natures so you can rapidly breed Pokemon with lots of potential for destruction.