I have a routine for defrosting my car.
Set engine going and blowers on full blast directed towards the screen, full heat, aircon on, rear heater that also does the mirrors on.
Quick spray of deicer onto front screen and quickly scrape over side windows.
Once ice on front windscreen has started to soften, scrape off - alternate from sides to front for a minute or two until nearly done - you need to get the ice off the front windscreen as this slows down the demisting process.
Have blue roll in the car to wipe over inside of windscreen - don't make the mistake of using anything that's been used on the outside of the windscreen as it will be filthy and covered in deicer so will make the inside dirty and smeary too.
Final up and down of all the side windows to wipe off any residual ice on the sides and I'm good to go. It still takes about 5 minutes to defrost my car to clear windows, but I'm in a fairly elevated rural area so we have hard frosts here. This morning was quite a bad one.
Need to find the windscreen covers that I bought and never used.