if you have to touch the car when going to wash it,
two bucket method with grit guards will help you in the long run!
why are you putting wax into a foam cannon??
would deff reccomend using a nice sealant or Carnauba Wax
look into @stayfreshcarcare
http://www.stayfreshcarcare.com/
they have some nice products for a good price
when i wash my car, i try to not touch it as much as needed
but to answer some of your questions, yes you can pressure wash, ive never used meguiar in a foam cannon before, i usually use Adams or Chemical guys shampoo in an Uber Foamer
http://www.detailersdomain.com/Uber-...nt-_p_204.html
when it comes to air compressor, anything that can handle i believe around 700-2000psi max for a foam cannon
steps i use
Pre-soak (let sit for 5-10 minutes depending on how dirty the car is) but never let it sit in the sun and dry out, the foam should be falling off the car
rinse off the pre-soak
if i have to touch the car,, starting at the top of the car and working my way down (cleanest to dirtiest)
rinse once more
dry one panel at a time with a microfiber towel, i like to use the Uber Super Drying Microfiber Towels
and apply sealents/wax after the car is 100% dry
[ame="http://www.youtube.com/watch?v=yiGj5f0l5as"]Tutorial: how to wash your car (best car wash methods by Auto Obsessed) - YouTube[/ame]