You know how much I love Gtechniq G1 - i've been using it for the last 5 years at least and it lasts around 14 months on my car.
However, I've recently applied Carpro Forte to all the glass on our cars. It's much easier to apply than G1. Polish the glass with Carpro Ceriglass - the best glass polish, which will remove scratches out of your glass, buff off with ease (easier than G4) then ensure all oils are removed by spraying Carpro Eraser on the glass and wiping. Then apply first coat of Forte. In the same way as G1 except it flashes straight off as you apply. Apply to the whole windscreen then without buffing apply 2nd coat and then onto the 3rd coat without buffing. When you have completed the third coat, using the same make up type pad, go over the whole glass, in effect buffing up the glass and smoothing out any high spots but as it flashes off quickly there is nothing really to see. That's it. Job done. It's so easy and no arms like Popeye required. I applied one coat to side windows and 2 coats to rear window. Now I wait to see how long it lasts but it's said to outlast G1. So far, first impressions are good.
You get all the products you require in a little kit in a box. The smallest bottle - 15ml, has done 2 cars.