The Joys of Grinding and Humping

One of the techniques I used predominantly where I could never get much alone time except for at night sleeping (and even then you can't make too much noise) is simply grinding the bed until you orgasm.

I get a bunch of tissues or a plastic bag, later on in life I found a condom is exceptional for this technique, then I lie face down on the bed completely naked with the sheets completely covering me and I can grind and hump the bed.

This may take an hour or two to reach orgasm, but trust me it feels great compared to your average jack-off-with-hand type orgasm.
The tissues or condom should absorb the 'mess'.
You can pair this with lube for a slippery experience.
What turns me on doing this is grabbing and running my hands up and down my legs and my butt as it gets so sweaty, you can try and muck around with anything with this technique.