What are the steps one should take when trying to verify the originality of a given blazon?

As an example, I translated the blazon gules on a pale argent a gauntlet sable into both Spanish and French and then did a Google search (found nothing). Where else can I go to determine if this design isn’t already in use?

I would break apart the elements of the blazon; a direct translation isn’t likely to match the syntax of how things are blazoned in other languages.  I’d work from Google Books and look specifically at Rietstap; not sure if the great German collection by Siebmacher and the printed editions of the d’Hozier Armorial General de France. See the bibliography at http://heraldica.org/biblio/annotate.htm#armorials for other sources.