Question about the silver lip

To anyone who has painted their wheels themselves, how do you make the silver lip so it keeps straight? I've searched through the boards for anything I could think of about this subject so I think I've seen a fair amount of the threads on this subject, but I never found anyone who included a How To or any details about how they marked the silver lip so it remains straight and even across the whole wheel.

Any information is appreciated.

 

http://www.tacomaworld.com/forum/wheels-tires/51358-painting-stock-rims-easy.html

This is how i painted my rims. Not sure what you mean by the silver lip?

 

Here are a couple shots from Ghost96Romeo's build. He's got, at least in the close up, what looks like a pretty close to perfectly round lip marked off.

 

tape

 

Buy some fineline tape from auto paint supply store.One Eighth of an inch wide should be good.