INSTRUCTOR WITH SPI TAXIES ACROSS RWY WITHOUT ANNOUNCING HIS ACTIONS AT A NON TWR ARPT. A COMMUTER ACFT LNDG USES HVY BRAKING TO AVOID CONFLICT.

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WHILE TAXIING TO THE ACTIVE RWY 35; I CROSSED RWY 12/30. I WAS LOOKING FOR TFC AS WELL AS MY STUDENT; FROM THE TIME OF START UP TO TAXI IT WAS ABOUT 4 MINS AND WE DID NOT HEAR ANY OTHER TFC ON CTAF. WHEN XING RWY 12/30 WE SAW LNDG LIGHTS AND THEN A VOICE ON CTAF SAYING 'HEY; USE THE RADIOS MAN.' THEN WE KNEW THERE WAS SOMEONE LNDG ON RWY 12. WE WERE TOLD THEY HAD TO USE HVY BRAKING TO STOP TO AVOID US. I BELIEVE THE CONTRIBUTING FACTORS WERE LACK OF COM ON CTAF BY THE LNDG ACFT BECAUSE HE WAS LNDG ON THE WRONG RWY -- WIND WAS 350 DEGS AT 10 KTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE DOES NOT USUALLY COMMUNICATE ON CTAF WHILE TAXIING. HE WILL DO SO IN THE FUTURE. OF COURSE HE BELIEVES THE OTHER PLT COULD HAVE RPTED POS ON APCH AS WELL. RPTR MADE A FAST TAXI AND EXITED THE RWY IN AMPLE TIME TO AVOID A MAJOR PROB. HE DID INDICATE THE COMMUTER PLT WAS PRETTY UPSET; BUT THERE HAS BEEN NO FOLLOW UP. HE DOES OF COURSE KNOW THAT THERE IS NO RIGHT OR WRONG RWY TO USE AT A NON TWR ARPT. HE IS NOT SURE IF THE COMMUTER ACFT WAS MAKING A STRAIGHT IN APCH BUT BELIEVES IT QUITE POSSIBLE.