Unsurprisingly it fucking stinks when you take your knob out of her arse. You'll probably do it once and wonder why you did afterwards as you wash your shitty cock.
If the girl had taken care and time to douche, then it will be as clean as a whistle, no smell, no deposits like some are describing here.
You get a girl who doesn't know what she's doing, it will likely be messy or sore for her. Non-satisfying to you. That's when YOU need to know what you're doing.
I've been lucky enough to take quite a few girls' anal cherry and I take everything in my stride. If it is her first time the whole ritual is part of the thrill of it.
I'll ask her to douche first. Even buy her one if she hasn't already got one. I'll give her a prolonged rimming, going from gentle licks to deep tongue action. Then some lube. The silicone based one is the best, and one then two fingers. Slowly deeper. More rimming, then more fingers. This time three if she can manage.
By this time I'm usually as hard as a rock, so I lube her arse, inside and out, and go in inch by inch, adding more line along the way.
Rarely is a girl so uncomfortable that she will ask me to stop, but it is amazing. When you are in her arse up to the hilt and she's playing with herself... Fucking hell, there is no feeling like it.