C.F.
I can tell you it's very child specific. My older son who is 5 now learned around 2, he picked it up very quickly and easily. My younger son is almost 3 1/2 and he still can't do it. With my older son we practiced with just blowing the tissue - you know making it wave in the wind created by blowing from nose or mouth. Once he got the idea of blowing through is nose then it was easy. Like all the other respones you have, you still have to hold the tissue.