The method that I have used to FF(force fetch) non-retrievers is a little different from some methods. There are two major differences that I have noticed. The first one is that I prefer to place the object to be retrieved in the dog's mouth by hand while giving the retrieve command TAKE IT. I will do this for 10 repetitions three times daily for one week. I do not use the ear pinch or any means of coercion until I have done this first step. If you have a non-retriever they really have no way of knowing what you want until you have done this step.
Once I have incorporated the ear pinch and the dog is beginning to understand how to avoid the ear pinch I proceed very slowly, starting with a 1 inch reach and again doing 10 repetitions 3x daily for a week before proceeding. Then a 6 inch reach, 1 foot reach, arms length reach, etc., you get the idea. Each progression is done for at least 1 week before going to the next step, and with the required repetitions. After you get to arms length, and not before, do you start to gradually lower the object to the floor.
Initially, as you get the object to the floor, keep your hand on the object and gradually remove it, this spot can sometimes become problematic for the non-retirever. As always do not hesitate to back up to a previous step if the dog is having a hard time of it.
The second method I use is different. Once I start to FF a dog I will discontinue any other retrieving activities. In my experience if a dog is really a non-retriever then it will only serve to continue to teach them the incorrect way to retrieve.
Once the FF period is over then we can start again to retrieve the proper way and get good fast, reliable retrieves and deliveries to hand.