I have the cleaning kits and following directions, they work really well. Make sure you order the right size kit for your sensor. There are some great youtube videos that show how to do it. Best advice on the swab sticks, don't push hard!
Also, instead of the white card, I did the following:
Nikon D7100 sensor cleaning, before and after.
I was astounded at the test shot of the before cleaning I did on that sensor. I was scared at first, but with youtube video help and my sensor cleaning kit, the difference is amazing.
I set the camera to ISO 100, aperture f/16 (highest for the 50mm lens), pointed at a blue sky and took two test shots. Then did the cleaning and repeated the test shots. In post edit, I set the dehaze slider in lightroom classic to maximum and that brought out every little spot and smudge like magic. This was a seriously dirty sensor, even though I had cleaned it last year once.
I hope this helps! I did one more cleaning afterward because there were still some areas that I wasn't happy with.
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