I've seen enough good artists at work to realize that projectors and tracings are not necessary to achieve what is commonly referred to as "realism." It's true that many artists do use them, but there are many who also do not. A good draftsman is actually slowed down by the use of "optical" aids.
As for detail, the general theory before the advent of so called photo realism has been that that the eye sees too much, that most of the seen detail should be left out of the work. Only the relevant and desired details are put in - they suggest the others if the artist knows what he is about.
If one examines a Bouguereau painting, there are a lot of details left out. On the other hand, one is not concious of the missing details as one would be with some coarser styles.