When I have had successful "assists", it's been after leaving them with a self made pip hole until long after I'm convinced that they are not progressing, and that they are not going to progress, often waiting until the next morning. By then, they're very glued in, the membranes are very dry, and they most likely need a hot tub experience to get freed from their membranes. At that point, there's no risk of them bleeding out! My first assist last year went on to become a very good layer. This year, due to a difficult hatch, I had to assist 3 or 4 to varying degrees, 2 required hot tubbing! And they are all doing fine. I consider the fact that they needed assist to be more of an aspect of my poor handling of the hatch than an inherent weakness in the chick. And I fully support the thought process that "an assisted chick" is not worthy of taking a place in the gene pool of the flock.