Some people strongly disagree with these ideas, but here are mine:
I've helped a few chicks break out of their eggs--I've had the membrane on an egg dry out and get too rubbery when the chick started a hole but didn't finish getting out for a long time, & other circumstances. If the chick is old enough that it's body has had time to absorb the yolk alright, and has pipped but is taking an unusually long time hatching, I feel alright about chipping away part of the shell to encourage it, or breaking off large pieces of shell or pulling membrane away if chick seems inescapably stuck.
When I helped a chick & felt it did not get enough correct exercise while hatching (because it didn't work at it very hard, or because the chick's position or the egg's condition didn't facilitate that), I've restrained the chick by cupping it in my hand (within the warmth of the brooder) for short sessions to encourage more healthy struggling and stimulation of muscle and organ development.
There is my experience for any who might be interested in the ideas.