Hi Su, first wet the whole car before you start this stops you rubbing the grime into the paintwork, then wash the car including inner door pillars & around the doors (Metal work) chamois the car dry this all depends on the weather, then as said use Auto Glym, Start at the front Drivers side work your way around, by the time you get to the front again you will be ready to polish off, regards the Alloys, this depends on how bad they are, if the dirt has built up & black marks left by the front brake pads you will need a good alloy cleaner, as I valet cars myself I use acid, this breaks down the very black stains left by the brakes, If you do come across Acid cleaner USE GLOVES, do not think that the job can be done ( As you state) showroom condition in 1/2 hr, the time taken to do the job right is approx 3 hrs that includes inside, if you can afford you would be as well to get the car valeted by your local valeter as he will have the right fluids to get the inbuilt grime out of your paintwork without damaging the paint & also the acid to do your wheels, to do the wheels right & this is what I do if requested, remove all the wheels + the spare depending on their condition they come up to my standards, Good luck & prepare for a sore arm!!