I would like to start by saying if you expect me to tell you that I found a magical glass cleaner that would guarantee streak-free windows and walk on water, that is not going to happen. Not even close! A great technical process is still important. I am human, have and still can be frustrated with this chore.
But I like Gyeon Glass enough to call it my new favorite and currently the only dedicated glass cleaner that I use.
About the technical process: Make sure you have plenty of good quality (glass dedicated) microfiber towels. Keep them clean/maintained. Specifically have at least one extra clean microfiber towel on hand, in case you don’t get the window perfectly cleaned. In other words, always have at least one more towel than you think you will need.
I have several of the Rag Company Diamond Glass towels on hand. Here is one below saturated with glass cleaner doing the heavy lifting, before I touch up the area with a second clean towel. I never want to run out of clean towels before my windows are perfectly clean.
Using the same towel, that is now dirty(see below), to chase after smudges is at the root of the majority of our frustration.
Already regularly using this product. I was given the task of removing the adhesive off of caked on duct tape from this vehicle (picture below). This car had duct tape bonded, in the Florida heat, for months. I started with the least aggressive approach necessary by using Gyeon Glass. I sprayed this product directly on the adhesive and let dwell for about 30 seconds before wiping with a microfiber towel.
It took 2 to 4 applications to remove virtually everything from each area, but it effectively got the job done. I had on hand razor blades, strong solvents that I did not want to use, and my polisher on hand to take on this task. Fortunately, none of those tools and products were necessary.
What I will say about Gyeon Glass is that it rewards a good process. It is a product I trust to help dial in the windows.