find an edge that you can barely hold with one hand in the crimp position and hang off it with all your might as long as you can.... shoot for 3-15 seconds, don't thumb over, just crimp. Do this once a week and you'll be crimping two grades harder outside wihtin a few months, also, you'll probably get injured.
Put both hands on the smallest edge you can in the open position and use only your fingers to move into a crimp position... then back to open then back to crimp... etc. .... this hurts even worse, have fun, do till failure then rest 10 minutes and do it again.
This is what people do who are mutants or not mutants but havent learned yet that this will get them injured.... I potentially have experience with this.
Bad long term game plan.