http://www.modelaircraft.org/PDF-files/706.pdf
Nothing specific on how to mark your runway from the AMA other than a "center line".
On any runway the centerline will be white. Most clubs will use a 4" wide paint roller, a line stencil w/ spraycan or an aerosol line marker.
Some just use a centerline if at all and some go all out with solid lines on the outside edges of the runway and taxiways.
Another suggestion, go on the AMA website and surf through the clubs. You will be blown away at some of the flying sites these clubs have.