Actually, what I find that works best for me, is to go to a specific subscription that I have, and do a search for the Surname only.
For census, I don't always know how the Head of Household was recorded. Some times its an initial, abbreviated first name, full first name. But by searching for the Surname, I'll see them. For non-census subscriptions, and search for the surname only, I'll see the Firstname list and go from there.
I do not think that the search engine at Genealogy.com works the way that you and I might think is should work. I have been successful in searching as I described.