first, it depends on your boat. what kind of boat do you have? A big river runner or creeker tends to punch through holes MUCH easier than a playboat..
Second, hit the hole straight on and paddle HARD all the way through. Lift your knees up to help keep the nose of the boat out of the water as you go through. Also, lean forward. paddle aggressively.
And last, if the hole seems too big, skip the dang thing!!!!
I am a class 3 boater. I paddle a dagger GT and it punches through all the holes I choose to go through. I skirt ones that seem like they will thrash me. Hope that helps!!
PS join our class 2/3 boaters group and come kayaking with us! the website is http://groups.yahoo.com/group/Coloradokayakers/