the ones mixed with feces are usually that evening when your food left overs are coming out with them.........
I just look in the evening and don't really hunt
the next day when it's all buttpee and clear I look and scoop.....
only the first time i had stones (my 4th or 5th flush) did I scoop some out and put them in a zip lock to show my hubby....we were so excited and that's when he started to flush......LOL some were the size of grapes!!