I'm now using Gtechniq C2v3 Liquid Crystal and using it everywhere: bodywork, glass, wheels and ok, even the house windows and UPVC frames - it's amazing stuff. Mix 1:2 to start and then follow regularly with a 1:4: wash, wipe, spray, and polish off with a nice soft micro-fibre cloth.
Kin-amazing' guys 
And I don't polish/wax, just a clean water wash and a flash/spray over wipe with C2v3 Liquid Crystal (all free samples gratefully received Gtechniq, no worries here, grovel, grovel, scrounge) - resulting in an amazing gloss/finish.
Clay? What's all that about? Used to make pots with that stuff back in the 60's. 