recently, after coming back from Scotland, I realized dirty sensors on my 800e and my DF
looking at some reviews I decided to buy the Eye Lead gel stick.
I found the following: on the D 800e I first was happy to get the dirt off, without wiping - you see the particles very well on the cleaning paper for the stick- then thought I made a small scratch into the sensor, then 2 , etc, until i realized it comes from the stick. On the Df it was much worse, the surface looked like beeing overlayed with a concrete pavement drawing.
So I went to the pharmacy and bought Isopropanol 98% and ordered Visible dust cleaners.
On wipe with them an the sensors were as clean as possible. So I still think the Eye lead is a good principle to take of "big particles" or spots and then clean with fluid.
On Photographers Life is this phenomenon mentioned for Sony, Fuji and Leica cameras as well...something I just have seen.