my old 106 gti was white. i used clearkote vanilla mousse. it's very very easy to use and gives as good, if not better, results that products like AG SRP.
i just went with whatever wax was most durable and long lasting... which i found to be p21s. dnt bother with sealants on light coloured cars. stick to some wax.
search for clearkote and P21s on ebay
there's a great ebay shop which sells it all.
also.... you'll always struggle to see any product on a white car. the clearkote stuff is a sorta creamy colour though so u do get a bit of a chance. lol. make sure ur using applicator pads too.
hope this helps.