I've spanked a few girls, especially if they're in school uniform and get into the role-play, calling me sir etc.
I always feel a bit self conscious when doing this, as I've never had any formal training as it were in how hard to spank, whether I could use something else etc. I suppose it's my fault, I should just be asking the girl. I think they've all been quite happy to take it, one of my regulars is quite sub and she does seem to get turned on by it.
I've recently been looking for a specialist sub and have been perusing Spankeefinder and other sites looking at a few profiles.
They all say, no sexual services are offered. So, I have 2 questions for guys with experience of this.
1 When they say no do they mean no or maybe? (As in massage with HE)
2 If not, what do I do with a raging boner when I've spanked her?
I was thinking along the lines of getting her to stand in the corner while I knock one out looking at her red bum. Would that be acceptable? My ideal solution would be for her to give me a BJ preferably with her hands tied behind her back! 
I think this all sounds perfectly reasonable. If I'm on an extended Dom/sub session I often get the girl to kneel with her hands bound behind her back and head bowed, while I punish her for any 'mistakes' made. Usually I'll be playing with a bit of orgasm denial, where she needs to beg me to cum, and girls that are into this get almost overwhelmed when I allow them to orgasm.
If they cum before I say, they get a bit of punishment. If they forget to say please or thank me afterwards, they get punished, etc, etc. you could do the same with the girl in a corner.
But!.... And here is the critical thing!
This is play and nothing more. It involves a detailed conversation. With the girl to find her limits. Believe me, if she is a good sub and you approach it in a matter of fact sort of way, and obviously not calling her for a cheap thrill, she'll appreciate your time taken.
Further to that is the conversation about when she says 'no'. Obviously in any other context that is not Dom/sub, no means no, every single time! With domination this why the use of safe words is essential.
I discuss with the girl beforehand and operate a three colour system.
If the girl says no colour at all, I assume it I a green light to continue. If she says 'amber' at any point, I agree with her beforehand that this means 'I like it, but just proceed carefully' if she ever says "red" that really does mean no, and I stop what I'm doing instantly. No ifs, buts or arguments. This is her absolute power over how the session goes and it has to be respected 100%.
If you play like that, then she can beg, protest and scream for mercy, but still have total control.
Really in Dom/sub games the girl should always have the ultimate power to stop or proceed.
Hope that helps a little.
