How do I turn a geneticised townie-friendly skin into a custom skin?

[funcioná!!!]

I downloaded some fantasy skins, but they are townie friendly and I don't want townies with those skins. I want to make them custom, as the creator didn't make a custom version. I have SimPE installed, even though I don't know how to use it. I looked for tutorials, the only one I found was the one from BogSims, but I searched it in that site and it's not there. Can somebody explain me how to do it, please?
Thanks.

[mangaroo]

Follow this tutorial in reverse: http://rikkulidea.livejournal.com/23079.html

Change genetic to 0
Change flags to 0x00000008

[funcioná!!!]

Thank you. I don't know why I didn't find that tutorial.