Hi Jerry,
Ny-rod works well in some cases but will expand in hot weather and change your trims.

The most common push-rod is the wooden dowl type found in most ARF"s with the threaded ends at the control surfaces and "Z" bends at the servos, you need a good pair of "Z-bend" pliers in your tool box anyway.
Carbon fiber rods are next, light and VERY strong with NO flex but these take a little expertise to work with and last forever.
You can also use aluminum arrow shafts, these come in smaller diameters as well and fiberglass arrow shafts.
Then we have "pull-pull" cables, most commonly used on the rudder and tail wheel. Very light, easy to install and rout (once you've done one their easy) and available in cable, carbon fiber thread or nylon. The cable type is available coated with nylon or plain, I use U-control cable I buy a swap meets and small diameter copper tubbing cut to 1/8" (or a little longer) for the crimps.
Hope this helps.
Chuck