As an elementary counselor and a mother to 2 DDs, I find myself recommending Jim Fay's Love and Logic most of the time. He has a great website (just Google love and logic) and you can find his books on
amazon or in bookstores. They are fairly reasonable and VERY easy to read, not too long or boring or anything.
On his website you can order CDs to listen to in the car (how easy is that?), and he even offers parenting seminars. I have even caught him on public television, and on his website he has a link to pbs where you can check out his seminar on discipline.
In my experience, parenting problems often arise because: 1) people try to be friends with their children instead of parents; 2) parents do EVERYTHING for their kids, overindulge them, and make excuses for them-never letting them understand real world consequences; 3) inconsistency and lack of follow through; 4) just plain old not knowing what to do
1) Trying to be your child's friend--Often the parent who wants to be seen as cool by their kids and their kids friends. BAD idea! Your child needs a parent to guide them through childhood and adolescence, they have enough friends! You can be friends when they are adults. This one is so dangerous, because your kids don't have anyone telling them "No", so they are constantly pushing the boundaries further and further, only to find there are no boundaries.
2) Parents who do EVERYTHING for their kids, give everything to their kids, and make excuses for them--these parents are the saddest, because they think they are HELPING their kids, but you are just hindering their growth (maybe because you can't let go and like to feel needed

) These parents don't like their kids to face any consequences or pain, but they don't realize they are creating manipulative kids and creating kids who are unable to deal with real life. They can't learn to make good choices if they never experience any consequences to their behavior. I know it is hard to watch your child be sad or suffer consequences, but it DOES help them learn and grow so they are able to make better choices.
3) Inconsistency and lack of follow through--this is easy to do, because parenting is hard! (especially if you have a high maintenance child). We all lead such busy lives now (our kids do so many more activities than we ever did) and we are tired! Sometimes it just seems easier to give in then to stay strong with what we know is right. However, inconsistent parenting creates a confused child who isn't sure what his/her consequences will be. They know if they push hard enough, they will win, and they usually do. These parents often resort to yelling, but it doesn't work. This one is hard to turn around, because when you finally bite the bullet and decide to be consistent, they will test you, because they are used to winning. It takes a lot of patience.
4) Just not knowing what to do--this one is easy to change
Try a parenting class, a Love and Logic Book, a Positive Discipline book, or 1,2,3 Magic. All are good (of course my personal fav. is Love and Logic)
Keep in mind, whenever a parent changes their parenting strategies, kids will sometimes rebel at first. They are testing you, so stay strong. Once they realize you mean business, they will come around. Consistency is KEY!
Good luck and happy parenting
SPECIFIC re: the bath issue. I would tell the girls as soon as they get in, "I will be back in 5 minutes to see if your hair is washed. If it isn't done, I will wash it for you, the bath will be over and you will be going to bed". Say it in a VERY NEUTRAL tone, no nagging or yelling. I suspect the first time, they won't do it (testing you, aren't they clever). Too bad they don't realize you mean business
Come back 5 minutes later. If their hair is dry, be empathetic. "Oh, what a bummer. I see you've chosen not to wash your hair on your own." Promptly wash their hair, drain the water, and off to bed. If they complain, "I know, that is so sad, I know how much you like playing in the water and reading books after your bath. I hope that tomorrow night you decide to wash your hair so that you can play and read books." You have to say this in a TRULY EMPATHETIC tone, NOT condescending or accusatory. Don't argue, don't nag, don't yell. Continue to be empathetic, and promptly stick them in the bed. They will be surprised. Surprised you remained calm, surprised you followed through, and surprised that you WILL remain consistent. The hardest part of this kind of parenting is remaining empathetic and neutral and thinking of of the consequences...at first. As you continue to practice, it gets easier and easier until it is second nature. Believe me, I have seen this type of parenting TURN FAMILIES AROUND! We can't change the kids, we can only change the way we are reacting and responding to them.