You may want to get something between a Trainer and #1 or #1. Biggest improvements for me came from forced closes, negatives, and timed holds. Doing grippers about twice a week is plenty, even once a week is good if you train with intensity. Though keep in mind that your grip training should be specific to your athletic goals. (so that finger board or block lifts will be more useful than crush strength training for things like climbing)
If you dont really care about damaging gripper, you can also file inside of the handles for longer ROM.