This morning I looked again at the finish I'd got after primer coats and decided that it wasn't good enough. It had some small holes along the nose so I tried to sand them out. Got some of them out but decided to try a skim coat of filler to fill them.
This was OK but it took a long time to sand that filler back level and smooth.
Put another 2 more coats of fill primer on, sanding between and then went over the whole lot with some 350g paper. Had a funny dimpled finish which, not until later, did I realise that the demon condensation was back.
Put two coats of colour on and left it for a half hour.
Coming back to it the moisture 'flush' had struck. Tried heating but it only made it worse. A light spray with thinners was the best solution.
I swapped to the bigger gun and although I was getting some orange peel, the moisture problem seemed to go.
I laid on 3 to 4 coats, waiting about 15mins in between and I was getting good results. The compressor doesn't quite deliver enough air for this gun but It works ok if the passes are not too long.
After letting the bonnet dry for a few hours, I put it back on the car.
There are still some marks from the filling and sanding but I'm sure some compounding and polish will get them out.