Gtechniq is available direct, they have great shipping rates, but their prices are about to go up further this month (May).
Back on track, I like Aquapel over G3/G4 and CQ on glass. I assume the OP may be referring to some of our threads where we use OC/CQ/C1 but Aquapel on the glass. Although I believe OC will last longer than Aquapel, I feel Aquapel makes water move faster than any of the others. A good 4 months, decent 6 months, and sometimes even after a year Aquapel performs. On my Audi, the G3 stopped shedding as much as the Aquapel after 3 to 4 months. Right off the bat, day 1, Aquapel still shed water more than G3. Of all others, G3 is the most shedding.
If you find a good deal on Aquapel, $5 can coat front and back windows. The best price I have found it is just under $4. Of course if you already have CQ/C1/OC and have some left, definitely use it on the glass. Any of these products will blow your socks off! So you can't go wrong with any of them. The difference is simply astonishing. Try one for awhile, then change up when you get new products.
Another thing I like about Aquapel is it has its own applicator. Use once, throw away. What I don;t like about it is that you have to be much more careful around the window seals than the others. All the others are safe on paint (made for paint!) where the Aquapel is not. I assume it is silicone based, so I keep it away from the paint and seals very carefully.
Bottom line, although I like Aquapel most, IMO it is not worth going out of your way to get some if you already have CQuartz, C1, G3/G4, or Opti-Coat.
The solvents will clean off anything still on it.
