I find it difficult to cum from oral most of the time. It feels great but the inconsistency of what she does gets me going then drops off if she changes it up. I need a constant speed and feeling for me to actually cum which isn't interesting to her while she's performing the deed. That doesn't bother me much at all but if I am indeed going to try and cum I literally have to create a sensation that I'm in control which means a little bit of thrusting or humping. If I have this control then I control the orgasm. So yeah, holding the head gives me this feeling when I hump the mouth but I am gentle with it. Not like a face fuck or anything.
My wife loves to have her head held in one place while the guy fucks her mouth but doesn't like him to push it deep when he cums. She likes just the head in so that she can taste his cum and feel it shooting onto her tongue. And yes, she always swallows.