I think that there are times to assist and times not to assist hatch. If they have pipped, give them 24 hours to try zipping. Usually, they can help themselves out in that amount of time. If not, there could be something wrong, such as being shrink wrapped or just not ready to come out. But if they are making slow progress, they should just be left alone. As long as they have oxygen to breathe, they should be fine. When there is bleeding, it means that the veins haven't receded enough for the chick to come out, and likely, they are still absorbing the yolk, so it's best to leave them alone. I would suggest wrapping the egg with a wet paper towel to keep the inner membrane soft and moist so that they don't get shrink wrapped.