I hope this post is not inappropriate....and maybe my small-town ignorance is showing. I have a real tough time with anything "covered" and while no sp or client in their right mind would ever do the "wild thing" without a glove, what are the dangers (both ways of a BBBJ) My search skills need a little work so if this is already a thread somewhere and I did not find it, my humble apologies. I've seen so many posts that a little research would have answered. I hope this is not one of those.
I used to have the same worries as you do. Long story short, the risk is there, but low. If you want avoid the possibility of getting infected, get a regular partner. Go with well-reviews agencies or independent,because girls work there usually take good care of themselve. Nobody wants to get sick, especially the girls, because they make livings out of their bodies.
Even CBJ has risks too, I guess you had read the majority of materials on 'oral sex'. You have to understand every STD, particularly their explicit symptoms, this would help if you see a cold sore or lesion on their genitals or mouth. However, some STDs don't have symptoms at all in women. So, no clues to find out.....
Don't get paranoid,dude. Everyone take risks everyday, you can lower the possibility, but in no way can you avoid any.