Wholeheartedly yes :) when I was a Teenager and my first job was working in a University Bookshop as a section Manager, one of the things I felt important was to be able to converse with my customers on the subject matter that they were inquiring about, so I was fortunate to read a lot of books. The sections that I managed were, Anthroology, History, Law and Politics.
I became quite converse in those subjects and was able to help my customers select appropriate texts for the work they were doing.
Point being - when you know the product you can talk about the product from an informed position. and there is no other position to have if you are going to promote that product.
Only snake Oil salesmen sell products they dont know anything about from experience