Several threads on these forums about this topic. As a starting point, look here, maybe, following some of the cross-links, and/or conduct your own forums search about sensor cleaning:
Gel sticks for sensor cleaning? - PentaxForums.com
Personally, I haven't found gel sticks to be all that effective, or prone to create their own problems (gel residue, "distributing" specks instead of removing them, even if you take care to stamp them off after each cleaning step). But others seem to swear by them, and it may well be my lack of skill in using them.
Cannot recommend VisibleDust swabs and cleaning fluid either, since even trying to use them according to instruction, I ended up with smears on my K-3 sensor. (I do recall that the tiny vial in my mini set made it next to impossible to limit the amount of fluid applied to the swabs to a single drop, so that I went through all the swabs in the set that I had picked up and still saw those smears.) What finally did the trick for me, and did so 100%, were the competing VSGO products:
amazon.com : APS-C Frame (CCD/CMOS) Digital Camera Sensor Cleaning Swab Type 2 Cleaning Kit (Box of 12 X 16mm Swab + 15ml Sensor Cleaner) : Camera & Photo?tag=pentaxforums-20&
Rollei seems to sell the same product with their own branding:
amazon.com : Rollei Sensor Cleaning Set APS-C - for professional wet or dry cleaning of cameras, vacuum packed and dust-free, white : Camera & Photo?tag=pentaxforums-20&
And, yes, DSLR mirrors
are still quite delicate. If there was anything minor on mine that didn't go away with a super-clean-and-gentle sensor brush, I would just leave it there, since it doesn't affect the image.
Disclaimer: The above are just my personal recommendations and preferences, based on personal use. People's mileage will vary.