The best process I have found for cleaning the "sensor cover glass" on a Phase One Back is to use the Leaf wipes with the Phase One cleaning solutions.
Phase makes an A and B, the A is blue and is only needed when you get a stubborn stain on the sensor. The B solution is similar to eclispe in that it dries very quickly and won't leave a smear.
You can use the B solution 90% of time, usually just one set of passes does it. If you use the A solution, you have to then use the B solution. A will streak when used.
The Leaf brand of wipes are like no other material I have yet to see and I have looked at most of them, Visible Dust, Eclispe Pec Pads, and the Phase One branded wipes. All of these wipe are made from materials that will come off and end up on the sensor, they are more course also. The Leaf wipes are amazing in how well they work. The leaf material will not streak and is excellent.
You can get a Phase One kit from any Phase One dealer and most of the same dealers will also have the Leaf wipes.
Paul