For a number of years, we have used and promoted the use of micro-fibre cloths to clean windows. This works extremely well with window film, as well as plain glass. As a bonus, fantastic results are achieved on mirrors, TV screens, stainless steel fridges or oven, as well as any smooth surface.
The reason we use Euro Cloth over any other brand, is the value we get. A good quality micro-fibre cloth is not cheap, but does the job. We have tried other, good quality cloths. They are usually half the size of the Euro Cloth. We have tried cheaper ones, bought at a Supermarket. Ok results initially, but very quickly, they lost the ability to absorb dirt.
Euro-Cloth is the only micro-fibre cloth with a 1-year warranty. It is sold in some shops for up to $56, we sell it for $35!
Now, here is a free tip: Never clean glass in the sun, unless you like a streaky finish!