I use an 8002
Used to use an '01 but found them too temperamental. Once you've used a pin to unblock such a small jet a few times, it knackers the fan pattern
If you use big jets you'll probably over-use product by a considerable degree.
My technique is to hold the jet further above the carpet than for pre-spraying when cleaning. I go quite a bit faster as well. I use the method of north-south then east-west - this gets it nice and evenly applied. It's best to find yourself with a little left over and quickly whizz over it again to use up the last bit, rather than run out after 3/4 of the carpet and then either be in trouble or use more protector than you thought.
On a new, dry carpet it needs to feel damp but not sodden. On just-cleaned carpets it will obviously mean the carpet is wetter than you'd normally leave it after cleaning. I always try to speed dry carpets I'm cleaning as much as possible before protecting.