It's hard to get that right, but the only way I know to try is using some of what hair people use called pinking sheers and I have some scissors that are a lot like that so that a cut doesn't cut all at once so you can make several cuts in different spots to get some what of a tapered look. I think it's harder with thicker less flexible materials too. I have not done it yet, but I think using some of the EP silky Fibers may be easier to try that. The scissors I have are Millers and has teeth separated with gaps and even the teeth have a V cut into the flat spot so none is really flat. Boy I hope I am not just making that harder to understand what I mean. If I need to let me know and I will take a picture of these. I think they are actually used in grooming pets. Ah found a picture on line and also they have some with both blades like this toothed one and I may get some of them too.
DUBL DUCK - Duchess Thinner - 30 Tooth Single

The double ones I don't have, but look like they may work better??
DUBL DUCK - Duchess Thinner - 30 Tooth, Double