You can cut off the tip of the post if it is way too long once your job is complete and fully taped. Just be SURE you do it in such a way that you don't get the tip of the ear too. If I have to adjust the length of the post, I put my thumbnail on the tip of the ear, making sure that I can feel the end of the ear with the ball of my thumb and that my thumbnail overhangs the ear tip, then I cut a little bit higher than the tip of my thumb. I make extra sure than my dog is staying still before I cut and that there is no chance that he will suddenly wiggle as I cut. In other words, I need the dog to be calm and accepting of what I am doing at that particular moment before I try to trim the post.
You can also measure the length of the post before you put it in, notice whether it is too long and by how much, once your pup is posted, and then use that as a guide the next time you post.
I'm not sure what mean what you mean about pushing the post in vs pulling the ear up--but basically you want to hold the ear between your fingers and thumb close to the tip, stretch it into a straight line above the dogs head (perpendicular to the top of his head) and then push the post straight down into the ear canal with your other hand, twisting it as you do. You can't damage the actual ear canal/eardrum because the ear canal turns toward the dog's head (almost in a right angle) so there is really no way you can push it in too far. Go ahead and get it snugly in there.
Stretch the tip of the ear upward from the dog's head with the forward inside edge of the ear along the post in a straight line.
DON'T let go! Press the ear leather up against the sticky post. DON'T let go! Start wrapping the tape around the ear, base and tip first (I *think* I usually put on the base first??.) Put the tape on fairly loosely and then squeeze the tape so that it sticks to itself and to the ear; that will keep you from putting it on too tight. The middle tape can come last; you can even let go of the ear for a second when you have the upper and lower tape in place if you need to adjust your grip somehow.
Your lower tape should start as low as you can get it on the post. Angle it slightly upward as you wrap it around the post toward the top of the dog's head (between the ears), but keep the edge of the tape as close to the top of the dog's head as you can. Wrap it around the back of the ear, about the middle of the bell or lower, then across and at a downward angle back to the post again, as far down as you can get it.
In general, if you have the post in snugly and the ears pulled up straight while you tape, when you let go, the ears will fall naturally into a slightly tipped outward position. \_/
If they tip inward, you need to redo your posting job.
I think perhaps if you are having trouble with the ears falling to the side too much, you are probably not pushing the post into the ear canal enough, and/or taping the lower tape straight across the ear too high up, rather than angling it downward when you stick it to the post.