I know BBFS at semi-legits don't happen frequently but I have had BBFS and BBBJ, often at the same time, at a number of well known semi-legits. I prefer semi-legits because I can get a good massage, ladies while older are generally cleaner, and it's just more exciting to get them to do more than is expected unlike at FS place where you pay more to get more and the expected nature of the FS services takes the excitement away somewhat.
The most recent one I had was with a milf MPA with big tits where I started with a massage, then she kept on saying I look fit and good looking so I complimented her back a bit just to be friendly. Well afterwards things got hot and transitioned into some intense DFK, then I told her to kneel down and open her mouth jokingly, to my surprise she actually obliged and got on her knees and opened her mouth. That's when I slid my cock in and literally face fucked her for a while. Then I told her to stand up and bend over where I started tapping her pussy with my hard cock, she was wet and I can tell her she wanted it even though she playfully said to be careful, I just shoved my cock in and fucked her and can tell she was pretty horny. We tried a few positions, then had her to suck me off some more, before I blew a big load.
I've had BBFS at least 5, 6 semi-legits, I think I generally hit well with ladies at semi legits because I'm a clean, fit and decent looking guy I guess. But damn, some of these ladies are pretty horny and if you learn how to talk with them, they will open up their mouths and pussies no problem. I didn't pay extra for those BBFS/BBBJ sessions either, just the regular room fee and $50 to $60 tips that one normally pays for a topless HJ. The ladies never complain and seem happy.