I cleaned a 108 inch wide 2.8 gain high power electrol screen today (before putting it up for sale).
I used a microfiber cloth a bucket of warm water and a big drop of dish soap. I very lightly "flooded" the screen...I.e. Made sure the entire surface I worked on (I did it in four strips) was completely wet and the water evenly absorbed...any oily spots are immediately noticed as they don't absorb the water/soap solution evenly. I tried to work the entire strip evenly keeping it wet. The dirty parts eventually became saturated and the oils were lifted. I took about 1.5 hrs to do this as I made certain to fight the urge to scrub hard. After doing 2 strips (half the screen) I washed the bucket and micro fiber cloth, ran fresh warm water , no soap) and went over the half just washed, ending with a fairly dry cloth and continuous stroke. Anyone who is fussy with rolling on paint will understand What I was trying to do...keep all finish strokes the same and the entire section evenly wetted.
I had tried spot cleaning one mark before...and I could notice the larger clean section...after an hour of drying...the screen looks great! I had maybe 5 or 6 spots and 2 streaks (don't ask...cause I have no idea ...perhaps beer?!). It appears only one small spot about the size of a pea is still visible and I will feel much better about selling it! I will report back in a day or so after watching a movie...but I am quite confident!