I've heard of "breathing the baby out" as well. The force of your uterus as it contracts really can birth a baby on it's own. What a wonder our bodies are!!
I had a pretty nasty epis. with a tear extending to the side and down with the birth of my 1st. Not quite a 4th degree tear but pretty gnarly.
With birthing Gabriel the last time I was pretty freaked when he started to crown. It was all together a new experience... DS #1 had been born with a vaccum and DS #2 was a c/sect. I swore i was going to tear any which way -to the front, back and sides. BUT my MW was good about using hot compresses (which felt SOOOO good) and a little olive oil to help lube everything up. Gabriel, weighing 10+lbs with a nuchal arm, came out without incidence. I tore a *little*. Required 5 stitches total and was feeling like resuming (a-hem) marital relations with DH within 2 weeks!! Which was soooo weird for us since after DS#1 birth it took over 4 months for me to even think about sex and then another 2 months before I could even handle (TMI sorry) full penetration because of the damage to my perineum.
I'm going to try for a water birth which I have heard helps naturally support the perineum (Michele Odent, I believe said that) and be a lot more calm with the pushing phase.