how do you spread coraline algae?

Will the coraline algae spread on it's own?

Unless it's unhappy about something, yes.

How fast?

That really varies with species. With my fairly new tank it spreads to new rocks very slowly, but then the initial spots have doubled in size every few weeks. They are still pretty small at this point though, with most spots on new rocks pencil eraser size or smaller after about 2 months. Also, some corallines are low light and some are high light. They are a really large group of species. However, I have not been taking the various special steps to accelerate growth.

Is there anything else I should be doing?

Most important is to make sure your pH and alkalinity levels are in sync with your calcium levels. If the new growth is very slow or dull-colored, consider testing for and dosing magnesium. Another trick is to make sure the coralline rocks are in heavy current to spread the spores around more. You can also scrub bits of coralline on the rocks lightly with a toothbrush to get flecks of coralline floating in the current without killing the source coralline.

Ideal water parameters:
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

That link contains links for more info on balancing alk and Ca. I suspect coralline takes up some nitrate, but it doesn't need it to live. I would feed the tank just a little if you don't have any animals in there.

my buddy got some stuff from garf called garfgrunge. i dont know what it is or how it comes to you but his tank had really nice corraline algae in about 3 weeks. i think the site is called garf.org

Yep. It normally goes away as soon as they exhaust the free silica in the water.

Coraline algae prefers blue light. If this is a new tank and you want the coraline algae to spread you should only use your actinic bulbs and leave the white light switched off for the time being.

You can leave your actinic bulbs on 24 hours a day for the first month.