After my initial heart-stopping experience with cleaning the CMOS chip surface of my Digital Rebel XT, I did a lot of reading and bought another item. This was a package of Pec-Pads – a very high quality lens and surface cleaning paper.
This time around I wrapped a small (10cm x 10cm) Pec-Pad square around the end of a sterile cotton swab, folding it to make a small flat edge at the end. Applying some ultra-pure methanol to this (two or three drops), I then swiped it once over the CMOS surface. Only once – I threw the paper away immediately afterwards. I repeated this several times with similarly folded fresh Pec-Pads.
After about six swipes the CMOS appeared completely clean. It took six swipes to remove some particularly stubborn dust, but it did at last come off.
I was fortunate that I could do this in a tissue-culture hood – essentially a filtered, dust-free, environment. That's a luxury that most photographers – or many photo repair centers for that matter – are not going to have access to.
Having done this sucessfully without too much sense of impending doom during the process, I feel confident that I can repeat it. This is very good. 🙂