btw, with regards to undercoating in humid weather: it shouldnt be a problem. when youre undercoating (regardless of weather) you absolutely DO NOT want complete coverage of a mini. You want a light dusting all over, nooks n crannies included, but you should still be able to see the metal/plastic through the paint. This is best achieved by holding the mini in one hand and the can in the other, spraying in wee puffs, like an atomiser, and moving the mini round and about so that all the surfaces are exposed to the puffs. The spray technique is probly best described as: not "ssshhhhhhhhhhhhpppppppt", but more "pfft. pfft. pfft"
The key here is that the undercoat is not a colour base. It is just a surface for the subsequent layers of paint to adhere to, thats all. Once its undercoated, THEN you can worry about colour. Airbrushes are what you need if you want to spray a whole mini with a colour. Or a big brush
Spray varnish, otoh, is a pain in the arse, as if you spray it in humid/overly dry weather you get frosting effects. i.e. it loses transparency and looks like mould. Its v annoying. fortunately for me, my worst affected models are my nurgle marines, who have mould anyhoo
