I'm writing this mostly because I had a bit of trepidation at the idea of cleaning my camera sensor after reading about some of the horror stories people experienced about various products, and I wanted to share my painless experience. I figured I had nothing to lose since you could grow potatoes in the dirt on my sensor so before a professional clean I thought I'd give it a go on the basis that I couldn't damage the sensor with the proper tools. Alas, one swab both sides was all that was needed and my sensor is immaculate.
Tips: Do try a rocket blower first. I doubt it'll ever take all the dirt off a sensor, but if it takes just some of the loose particles off its less gunk for the swab to collect. The four swabs are individually wrapped. Unwrap them last and don't let them touch anything apart from the solution and the camera sensor. Open the solution bottle first, it's tightly closed! The package contains four swabs. Even with a sensor as filthy as mine I only needed one swab (both sides) to get it clean, so I think this package is enough for at least another clean or two. Put slightly less solution on the side of the swab you'll use second. That way you clean, then the slightly dryer side can absort some of the solution. I found the solution left a thin film on the sensor but it has dried streak-free. Don't bother with a loupe as some sites suggest. If you're sensor's dirty you don't need to confirm it with a loupe. Just pop the lens back on and take another test photo at f/22+ If the worst comes to the worst you won't damage the sensor (as long as you don't do anything daft) so if it doesn't work out you can arrange a professional clean, so it's worth a try.