If you can, use 'radiant' heaters, those ones that give a red glow or the new halogen ones. It's the surface temperature that requires raising for paint more than the ambient air temp. The radiant heaters will heat the surface quickly and the surface in turn heats the surrounding air.
As far as primers are concerned, I've always used 2 to 3 light coats of 'Bonda Primer' (red zinc oxide) thinned about 10 to 20% with cellulose thinners directly over cleaned bare metal and then a good coat of 2k grey 'filler' primer within 4 to 12 hours. I've also heard that 2k thinners can be used instead of cellulose in the Bonda Primer but I've not tried it and the manufacturer doesn't mention it in the literature.
Cleaned bare metal in my books is wiping down with panel wipe, then a rust killer like 'Jenolite' and then panel wipe again just before applying the primer.
If you leave the Bonda Primer much less than 4 or longer than 12 hours it can react with the grey and cause problems of 'pickling' or adhesion. Something about it being an epoxy base where solvent flash off occurs within 4 hours but the epoxy curing bit only gets going after about 12. If you can't get it covered in 12 to 24 hours it's better to leave it for a week or so then you can proceed with the upper coats without problems.
Editor of the VVOC Magazine ReVival
"When you have a Firenza like mine, who needs any Minis?" copyright David Maxwell 1979.
