When one FF's a dog, it is not to get him to retrieve but to teach him to bring it in every time. Not when the dog feels like it or when it's easy enough but when you want him to. The other point one can make is the dog handles discipline much better. This makes the dog more likely to accept the owner as the alpha. reading it in a book is not as easy as having someone show you how. A pro will get it done in two to three weeks. It will take an experienced amatuer trainer a little longer because most amatuers have a job and can't work it more than once or twice a day in their schedules. An inexperienced trainer with a very stubborn dog ( my first was a Ches) can take a long time (the Ches took 3 months). However you do it, however long it takes, just do it. The time is worth it. Not many dogs can perform in tough circumstances and finish if they are not FF'ed.
Dr Fatguy