If you haven't used a
6" wide Triumph Scraper, your missing out. The blades on these scrapers are so thin and sharp that they scrape better and easier than the standard 4" box store scraper.
I have talked with several glass guys and the key to not scratching the glass when scraping is to pick up the blade on the back stroke. Most of the scratches are caused by grit getting trapped between the blade and glass and getting dragged across the glass on the back stroke. It makes a huge difference. If your blade and blade holder is nice and flat, you typically don't need to worry about the corners digging in.
The liquid you use for scrapping isn't all that important. It's just there to keep the adhesive from sticking to the glass after you scrape it, and it will slightly soften the acrylic adhesive. I don't use adhesive remover because it turns the adhesive into sticky gooey snot and then you have a sticky gooey mess on your hands. I use alcohol because its handy and I'll use it to wipe the glass when finished anyway. If I had a lot of windows to remove I would choose soap and water because it's cheaper and doesn't dry/flash as fast as alcohol.