I buy the original product you put on by hand not the windshield washer fluid nor the option available in the car washes.
You start by stripping the glass 100% clean, then apply the Rain-X in a circular motion (wax on grasshopper) covering all the glass, let it dry to a slight haze and then wipe it off (wax off) with a clean dry cloth, terrycloth works best.
To make sure I got it all I wipe the windshield down again with a fresh cloth, you could consider yourself done here but.......
I repeat the process of applying the Rain-X one more time, wait again for it to haze before wiping it thoroughly clean one last time.
The result is NOT having to use your wipers during rain storms as long as your going faster than 20 mph, even if you're going slower the rain will just fall off your windshield like magic.
It's amazing stuff, you'll wonder why we're not required to use it regularly or why state vehicles aren't required to either.
When the rain hits your glass it beads up immediately instead of just hitting your glass and spreading out obscuring vision. because it beads up so perfectly you'll be able to see right through each little bead as though it were a lens. because it beads up each drop of water has less contact area w/the glass, this allows those beads of water to flow off the glass while under speed or just fall of if you're standing still.
a lot of what I say here might not seem to make sense, it's hard to describe succinctly but if you were to use this stuff and find yourself in rain you'd be amazed. the wipers were broken in my old Buick so I Rain-X'd the windshield, a couple of nights later we drove 200 miles round trip in the pouring rain to see a concert. My passenger Rodney couldn't stop yacking about the miracle he was seeing.......
