You do not want your flies (nymphs or wets) to spin !!! As everyone before me has said in a nice way, it is counter-productive. The materials you use in creating lifelike movement are more important; ie. rabbit, maribou, Ostriche (especially gills), Organza (the best material in my opinion for gills); pheasant for legs (Veli Auti) , or rubber legs.
How do each of these materials act in slow water, or how do they act in fast water ???
When you consider this approach, you will design patterns that are 100% more effective and consistently trigger strikes !!!!!