apparently sealents work best on metalic silvers as the pop the fleck out more.
the usual wax/ polish combo most will recomend for people not wanting to spend millions is SRP and HD wax both autoglym both with great reviews.
if your wanting something that will last ages then why not try something from the gtechnique range (albeit expensive) or eavn wolfs body wax
Im giving autobrite "to seal and protect" a go, lasts around 2 months brings the sparkle out on the metalic paint, gives a great finish and great beading/ sheeting.
the worlds your oyster so to speak pick a budget, read some reviews and have a bash!