I think you have to "wire up" your mind, and that it takes months, if you are studious and do a lot of sampling. Before this, I did a lot of cooking, including experimental stuff. I worked with a lot of herbs and spices, and tried oddball combinations. However, this didn't seem to help all that much with frags, probably because they are so blended, with a few exceptions. Also, I didn't know what a lot of notes smelled like, so perhaps if you already know the notes it would come more quickly.