During his career he has published several books and designed hundreds of coats of arms, flags, banners and seals for over 1000 different municipalities and institutions.

Since 1990, he was a research worker (scholar) of the Hrushevskyi Institute of Ukrainian Archeography and Source Studies, National Academy of Science of Ukraine.

Grechylo received his PhD in historical science in 1996 and defended a dissertation titled "Ukrainian Municipal Heraldry: Tendencies of Evolution".

In 2012, he defended a dissertation titled "Ukrainian Territorial Heraldry" and he was awarded the degree of Doctor of History (DSc).

In 1990, he has founded the Ukrainske Heraldychne Tovarystvo (Ukrainian Heraldry Society) – since 1995 a member of FIAV (Federation internationale des associations vexillologiques) and CIGH (Confédération Internationale de Généalogie et d’Héraldique).