I don't mix the Unger liquid with Fairy (just water
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I'll also use it in my sprayer for scrim work. If you can get used to using it without fairy its a real plus. I know that plenty of window cleaners put a drop of fairy in with the mix to help your squeegee glide over the glass, but I believe you are just negating the benefits of the specialist liquids (whatever make you might be using).
I know GG3 & GG4 are expensive, but as I understand it, it goes a long long way, I shall have to order some so I can try it out, I keep meaning to but never seem to get around to it!
Ian