Just to add my 2 pennysworth
We have painted several vans (sorry nowhere near Drotwich though) and over 100 classics.
Just like Barry & Chris say the key is preparation, preparation, preparation.
To illustrate its a little like painting a wall in your house, what takes the time is repointing the brickwork and plastering, putting the paint onto a mirror smooth surface is just the final step. Its getting the mirror smooth surface that takes the time.
2nd point: We once restored a 1920s car. The owner wanted it brush painted just as it would have been originally. We did all the prep but didnt feel confident to do the brush painting so got a guy in to do it. He did a great job, but boy did it take a lot longer than spraying, and he wouldnt even let us put it in the paint oven between coats.
So to summarise you can get a great job with brushes but it does take longer.
But in either event the prep must be spot-on. When its perfect by eye, then close your eye and see if its perfect by finger. Then put on a guide coat to see any other imperfections because any imperfections you see in a guide coat will be magbified many times by the gloss coat.
Cheers
Jules
RatSport www.ratsport.co.uk