It is really not difficult at all, and you can shoot any weapon well just by developing familiarity. It would be like saying one can't play football, baseball, basketball, or golf well if they try all of them. There is obviously evidence that one really can.
I shoot my longbows the same as my recurves, and I never understood why anyone would need a different grip on a longbow. They are simply bows that shoot arrows and can be shot the same.
And, with a little practice, you can shoot them all very well.