Never done this until the past weekend, but I wore one of them compression type moisture wicking tops (like you would use for on the mountain) under the 5mm. I was very toasty and able to stay out almost 2 hours. Only qualm might be that the salt water is no good for these synthetic fabrics....
I have never had a problem... I just go out. Had a friend that put Vaseline on his face- I don't think it helped. Just try to keep the back of your head into the wind