I think it's all in the technique of flat ironing...some serums work better for certain people...but its not ALL in the serum IMO...
Here's what I do
I wash with whatever shampoo
Then I deep condition with Pantene R&N mixed with my coconut oil/EVOO/and Sweet Almond Oil Mixture
I seperate my hair into sections with my big comb and comb some Chi Silk Infusium(Or your fav serum) through each section.
I put some spray on heat protectant on my ends...I use V05 Heat defense.
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The MOST important part is the blow drying. First I comb out my wet hair with the denman after it's combed out with the big comb
Then I hold each section of hair taught and blow out my hair 50%
THIS IS IMPORTANT
This part is where most of the straightening happens
Next I take my HUGE paddle brush and finish blowing out my hair. (Trust me, if you have combed out your hair properly you won't lose hair)
After that I rub A LITTLE Sweet Almond Oil into my hair for moisture and flat iron using a rat tail comb. By this point you will hardly need the small comb and it will glide through nicely. The flat ironing should take no time because the blow drying part does most of the work...HTH
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Also, this lady has an EXCELLENT tutorial...so great that I actually contacted her to do my hair and she's done it twice. She has pictures so I hope they help! You don't need all those high end products though...just use trial and error and figure out what works for you. Just don't forget moisture!
http://public.fotki.com/patchouli85/flat-iron-tutorial-/