A classic oldie is at the end of "Behind the Green Door" with Marilyn Chambers. The good is that it's a perfect example of what you're talking about - the guy's cock jerks and spurts four or five times with no hands or anything else.
The bad might be that it's all done very artistically, with slo mo, colour changes, mirror effects and so on. I really like it. Given that this was from 1972, it's actually pretty good special effects, let alone special effects in porn. It's the porn version of the end sequence of 2001: A Space Odyssey. If you've never wanked while stoned, this would be the scene to do it to.
Another hands-free effort is in "London Calling" from Private's Pirate fetish line. In the last scene a buxom blonde is taking it doggy style from a guy who is screwing her with both hands behind his back. When he comes he just pulls his hips back so his cock slips out of her pussy, thrusts forward again so his cock is over her buttocks and spurts three or four times over her back.

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