I like clear waxoyl....cheap and easily available. You'll need to check it over (reapply to some areas) every year or two though
The least messy way to do the outer skin is just paint it on then run a hot air gun over it which makes it wick...inner box sections it will need warming and spraying.
Things like dinitrol come up very good on reviews too.
There are mobile people who do it too...here's a link to one...
http://www.rustmaster.co.uk/