I have a (couple of) foam cannon, and a foam gun. "Cannon" generally refers to one you attach to a PW, "Gun" is one that you attach to a hose. I find they both have their pluses and minuses.
The cannon makes lots of thick, clingy soap and is more effective as a pre-wash, while the gun is much more "maneuverable" and can be used instead of the soap bucket.
If my car has a light coating of dust and hasn't gotten wet, then I find that soaping with the cannon and simply rinsing with the PW is the fastest, easiest way to keep the car shiny and clean. The key is this - unless a mitt has been used (and in this case I wouldn't), I don't touch the car to dry it - I dry with air. This method works well because my car has been CQuartzed - not sure that it would be as effective without it.
If the car is particularly dirty, I pressure rinse, soap with the cannon, pressure rinse, do a two-bucket wash, and then dry with a MF towel and some spray detailer. If you want to be really careful, the foam gun is great to lay down some soap right ahead of your mitt as you wipe. With this, you can take one of the two buckets out of the picture, and simply use a rinse bucket (with grit guards, of course).
I bought my first cannon from Aliexpress, and the next ones from Amazon.ca (I bought the second one because I caught a deal for $10 and thought it was worth it just for the spare parts, and the third I bought recently because I wanted a "shorty" PW wand and got the whole set for only $5 more). The first gun (which I sold because it sucked) was a Chemical Guys from Amazon, and I've replaced it with the no-name version of the Gilmour Foamaster also from Amazon. The second one is much better.
orange260z
2009 Porsche Carrera S Coupe PDK/Sport Chrono Plus - Porsche Racing Green / Sand Beige Full Leather
1999 Miata - Brilliant Black/Tan Leather