I've done it a few times before. I have to do it by cumming straight into my face/mouth though, I've not been able to just come onto my hand and lick it off (for example) as I usually lose interest straight after ejaculating. Also, I don't know whether it's just feeling stupid or feeling guilty, but I always feel this way after doing it. I'll turn myself on thinking about doing it but after I've actually done it I'll think, "Why did I do that?". Doesn't stop me doing it again and again though.
I do it pretty much the same way as you can see in Randolph's avatar; legs over the head, cum into face and mouth.