All things are possible
Not all Hunters are created equal. Some have particular affinities or talents which represent years of training, specifically cultivated skills, or specific attributes. While most hunters tend to operate as jacks-of-all-trades, others have a more narrowly focused concentration. While these skill sets, and training options are not exclusive to hunters, they are more widely available to humans and easier for humans to acquire.
Exorcists
Trained exorcists are individuals trained by the Catholic Church, and sometimes Lutheran Churches, authorized by the Holy Father to perform the Roman/Latin Rite of Exorcism on behalf of those afflicted with demonic possession. They are also some of the few individuals who know for a fact that demons are real. Exorcists in this context do not have a special power or a unique qualification beyond the power of their faith and adherence to the rituals required by their respective religions. While there are some among the hunters than can perform exorcisms, it is not entirely known how they are able to do so without being properly consecrated.
Armed Forces
Service in any branch of the armed services, US or otherwise, instills the virtues of self confidence, leadership, duty, and responsibility in those that come out of the Service along with weapon skills, armed and unarmed combat techniques, and other more specialized skills such as combat engineering, explosive ordinance disposal, demolitions, and others. As one moves up through the ranks, these virtues are built upon. For those that have served as part of a Special Forces team, SEAL, SPETZSNAZ, SAS, or any other elite unit, these skills are expanded and grow more in depth and are accompanied by a marked increase in level of skill and knowledge of warfare.
Intelligence Agencies
The skill sets developed and cultivated by Intelligence Agencies (CIA, MI6, etc) are varied and the people holding them can come from any number of trades, professions, and former occupations. Regardless of origin, there is an emphasis on macro and micro level thinking, situational awareness, critical and analytical thinking. There are of course Jason Bourne or James Bond style clandestine operatives, whose training is the stuff of speculation, countless movie and TV interpretations, and official inquiry.
Medicine
Medical expertise, regardless of origin is always a valuable skill. People with medical training have marketable skills in any economy, in any country, and in any type of situation. Hunters with medical training are often brought into the lifestyle by encountering something unusual or to treat victims of the supernatural. Knowing how to treat wounds inflicted by supernatural creatures or through magical means is a highly desired trade.
Law
A background in the legal professions, whether as an actual attorney or paralegal, are invaluable to the life of the Hunter, regardless of traditional or otherwise. Practical knowledge of the law allows Hunters to conduct their investigations more efficiently, blend in more seamlessly, and have a working knowledge of what is and is not permissible for federal agents to do.
Loremasters
Loremasters are individuals which have spent many years, sometimes entire lifetimes gathering lore about the supernatural world, and compiling this lore. Some maintain vast libraries, and others have stepped into the 21st Century and gone fully digital. Loremasters in particular have a great deal of esoteric information available to them, and for this reason are often valuable resources for hunters, and for others.