Didn't use an undercoat, as when I'd sanded off 4(!) Dysons full of household gloss, the paint underneath was sound. I thinned the black 50/50 following the advice of the various useful webguides out there (search on 'roller painting' or something similar - here's a couple I used:
http://www.volkszone.com/VZi/showthread ... 03&page=25 or
http://rollyourcar.com/default.aspx or
http://carpainting.wetpaint.com/page/Ro ... hod?t=anon or
http://www.theminiforum.co.uk/forums/in ... 632&st=315 - you'll find the American sites helpful except their version of Rustoleum is marketed under a different name (and they have a different name for 'white spirit'.)
The yellow was more problematic, giving lovely smooth glossy finish at 50/50, but it didn't have the 'covering power' (some of it was going over the original black, which was giving the yellow a 'greenish' tinge) solved this by using a first coat of a lighter yellow that I'd bought in error. (for some reason the lighter shade covered much better.)
The hardest bit is not being tempted to under-thin it (to get quicker coverage) if you do this you get a thicker skin that doesn't flat down as well (tends to tear off rather than sand down). It seems the most glossy coats (with the right ratio of thinners) go on with lots of tiny bubbles - which encourage you to keep rolling at them: don't - leave them and they settle away on their own!
The Nova has only taken about a week to do, mostly because it's a much simpler shape and I don't have to use access gear to reach the roof!
I've already bought white to do the traveller when I've finished (well actually started!) its restoration, and the Rustoleum red looks just right on Massey Ferguson bonnets - I think you can see I'm well converted to the system!
BTW, the van cost just over £60 in paint and thinners - the Nova has been painted with the dregs of the left-over black.....
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