These images are shot at a white door, flash, 1/60sec f/8. Each was brought in to Photoshop and Auto Levels was run on each.

Look at the difference, even with an amateur swabber like myself! The sensor was so dirty I could actually see some of the bigger dust specks. Instead of the rubber spatula, I used a covered x-acto knife, which turned out to be exactly the same width as Nicholas specified (14mm)!

Thanks a bunch to everyone who warned me. I took extra care and will continue to do so in future cleanings.