One way I have found to effectively smooth frizz, and give new life and shine to old tired doll hair is with a little regular shampoo and conditioner, and a regular curling iron.

 First, you may want to remove your dolly's head. If it is attached with a neck string, just untie the string.If it is attached with a plastic band, you may not want to remove her ead until you have purchased some more plastic neck ties to fix her with. They are available in the harware section in many stores.

 Taking EXTREME care not to get water near the eyes, wash the hair with regular shampoo, and condition it with conditioner (I use my Pantene). I know a lot of people swear by products intended for wigs, but I do not have any of that here, and I have used human products on all of my dolls for years and years without any problem. 

 While the doll's hair is slathered in conditioner,  use a comb to gently remove and and all tangles, starting at the very bottom of her hair and working upwards towards her scalp.Once her hair is tangle free, rinse it in very hot water. Rinse and rinse and rinse. Make sure you get all of the conditioner that you can out of her hair.

 Next,  pat her hair dry with a soft, clean terry towel.Never rub or scrub your dolly's hair, just pat it. You want to be sure you leave it damp- not soaked, just damp, for the next step. 

 Now, take a regular curling iron, and set it to medium head. My curling iron has 15 heat settings, with 1 being the lowest. I use it on 12.

 Test a small area of your doll's hair. Under the back near the neck is a good place to test. I have NEVER damaged doll hair with this method, but it is ALWAYS a good idea to test an inconspicuous area first. Better safe than sorry.

 If possible, keep a misting bottle of clean water nearby, you want to keep your dolls hair wet during this process. Remember it is DRY HEAT that does the most damage.

 Use a comb to separate out about a 1-2" section of DAMP hair. Starting with the curling iron at the scalp, clamp the iron onto the hair. Gently, slowly pull the curling iron down the full length of the hair.You should see instant improvement. If not, you may want to turn the heat on your curling iron up just a bit.Take as many passes with the curling iron as you need to over each section of hair. Repeat this process until your dolls whole head has been done. Repeat is necessary.

 Even though it may sound scary, this is a very easy process. Just remember to keep your doll's hair damp, and be patient. You should see an amazing difference!

 Here are some photos of the results of the same process used on Jumbo Braid hair from a beauty supply store.

BEFORE:

AFTER: