I have used trademark searches before, such as http://www.uspto.gov/ but each country has their own, which means more searching than I have time for. Besides many of those sites are incomplete, outdated, difficult to use, or all of the above. Is there anything more reliable than a common web search plus the word "font" (or whatever your product will be)?
Is there anything more reliable than a common web search plus the word "font" (or whatever your product will be)?
Not really. You can outsource the work to some 3rd party that can do this for you.
There is no central authority that can give you this info. Even exhaustive searches do not save you on a global scale. If web search is not good enough for you then you need to be prepared to send people to different countries. Even after this you can not be sure somebody can take the name meanwhile.