More effective than advertising through gifted programs might be to seek out schools without gifted programs and talk to the teachers. Where there are already gifted programs, you're less needed and will probably be perceived accordingly. In systems with no or minimal gifted programs, there will still usually be good teachers who have identified students who need more than they're getting. If you can find good criteria for identifying active "good teachers" and contact them selectively, you would do more good and probably attract more interest.