Guayar means crying, lamenting, complaining, suffering. Guayando is an inflection of that verb and means crying, complaining, wailing (It is in Gerundio). It also means grating or shredding with the grallo or grater.
See guayar ( infinitive ), guayando ( gerundio ) .
In general cool or guayando rather means to be sad and crying. In Puerto Rico it can mean from glued dancing to grating a carrot for example or scratching the ceramic hob.