Part of the problem, is the ring and little finger are no designed for dexterity. So when you integrate any of them to work with the Thumb, Fore and Middle finger, they will take time to come good, and they will of you stay with it.
There in lies the other part of the problem, why stick with it, when it seems to make things worse? Why do it when I am better with two finger?
Those questions will answer themselves if you stick with it. You cannot comprehend the benefit until you have mastered it.
So many players post about how they tried it and gave up, or it made no difference, or found it pointless. These player cannot give you the full picture because they do not know what the full picture is...they can only imagine or assume what the benefits may be.
Stick with it and what will happen is your tendons and ligaments around the little and ring finger will slacken off. When this happens you will have chance to then develop the dexterity to use it, then the co-ordination and strength to play bass with it. This of course takes time, and that is different for each person, because each person uses their hands in daily life in such a varied and diverse way.
If you practice and develop your hands for 2 hrs a day, life has at least 12 hrs to undo or be counter productive to anything you have done. If you have a job that is hand labour intensive, then 2 hrs a day may actually cause damage unless you warm up and get the hands ready to play, in other words take the strain of the daily use out of them before adding more to them.
If you have a job that requires heavy holding or lifting, then you may never develop any as the job will negate anything you do.
Say as a bricklayer you work 10 hours a day, then you hands are developing to work 10 hours a day to hold a trowel and handling bricks, not to develop touch and skills to play bass.
This does not mean you cannot, it just means you have to understand why your progress is different from others. There are a few great hand stretches that target the little and ring finger ( the Ulnar side of the hand, this is your hands power side, the thumb, fore and middle are the dexterous side of the hand and we call it the Radial side) in as much as they will help loosen the fingers to allow them to start to become dexterous. Once you have it mastered you just have to use it to maintain it.
http://youtu.be/Ab-dtzrAnkg