Where salt is present using Power clean dilluted 1:3 would be the desired method for pre-wash. Spray on, leave for 2-3 min and PW rinse off. Then do a normal ONR (or with whatever else you wish) wash.
You could still use Ferrex after that to remove iron contamination. If after that the paint feels smooth you could go straight to seal or wax.
Depending on where you live and how you drive you need to remove the following
- Tar spots...those black spots caused from agressive driving, fresh layered roads...for those use a dedicated tar remover or clay.
- Iron contamination...they are those rust spots caused by industial fallout (it will settle mostly on the top parts of the car) and braking (will settle on the lower side parts of the car behind the wheels (and on the wheels). For that use Ferrex. For heavy dutty contamination you can use Ferrex as clay lube. Ferrex will disolve iron and clay will aggitate it and pick it up. Just remember to do section by section and dont spray Ferrex on the entire car if you are gonna use clay for aggitating.
- Road film. Its grease and grime from the road (oil and gas mixture on the road combined with rain and splattered on you car as you drive over it). Clay wont pick that up or remove it completely so that is where Power clean comes into play as a pre wash.
- Water spots...caused by hard water. Use MDR for that.
All said and done I would still follow it with a light polish or paint clenser using OPT poli-seal or OPT Finish or Hyper polish before protecting paint. But thats just me.