I had a Canon EOS 20Da camera with something very tenaciously sticking to its sensor. Using a rubber bulb followed by Green Clean swabs, I got it clean. I don't have the full Green Clean vacuum kit.
Their liquid does not evaporate quickly; instead you wipe it off with the second, dry swab. That way it won't leave drying marks, and it stays in place, loosening up the crud, until you wipe it off.
I had to use all 3 sets of swabs on one cleaning of one camera. That's partly because it was an unusually gummy speck on the sensor. Always keep extra swabs because they're not reusable.
Be careful, of course. This is not for people who have never cleaned or repaired precision optics. I do a good many of my own camera and telescope repairs.
This works so well and without mess that for anyone on the road and with a dirty sensor...HIGHLY recommended.