I have checked the wiring, jumped the horns which sound great and taken apart the steering wheel. The horn relay is fine. Nothing seems to work. Is there anything else I can try before I give up?

you need an ohm meter so that you can do a continuity check and test your grounds. Also, if you have newly painted surfaces, then that would also disrupt your ground at those points...

This link to a horn problem diagnosis paper may be of help.

http://jimshea.corvettefaq.com/wp-content/uploads/2006/06/HornOperationDiagnosisACar13JN06.doc

JIML82