You can use Fairy Liquid etc to remove all the crap - layers of old wax, polish silcone shite etc.

I use it once every 6months or so to remove all my layers before i clay the paint, re-polish and wax.

If you use the fairy option you should use a decent shampo straight after to remove all the surfactants and rubbish (salts etc) contained in the Fairy before you start to use your products.

Then start your polishing and waxing after that.