As a mom of 23 yrs let me tell you I have had the same struggles you are dealing with now. :) The other poster had a very good point - consistency is the key.
When we swat bottoms (and I did until I learned another way) all we show our kids is that we can hit them - which many kids then turn around and use back on us or on others and then they get in trouble for hitting...very confusing for them - if mom can hit why can't I?
When we yell we have lost control and all we teach our kids is how to yell and that mom has lost control.
I have zero respect for the Super Nanny - She has no background in child development at all and I can't even watch her show she just makes me want to puke. I have a degree in child-development and she is no expert. She is simply a good babysitter who auditioned for a show and got the part. No kidding!
Now - what to do? I found a book many years ago that saved my life and eliminated the yelling and swatting and frustrations. And as a result, taught me consistency, and my kids to behave. :) At 12 and 14 (my 23 yr old is on his own - we didn't have this book for him and I really wish we had!) my boys are really well behaved and we have a fabulous relationship! :) The book is called 1-2-3 Magic by Thomas Phelan. VERY Good. I just got his one for adolescents - not because I really need it but because I figured my boys are older and it could be helpful. It has proven to be so.
Give it a try...it is worth it. It teaches the parent how to work with their kids different personalities, and how to stay in control of your own temper, how to be consistent and how to develop a relationship of respect with your kids...