I tried spray paint undercoat years ago and it turned out rubbish. It left a textured stippled effect on the models. I've not gone back, until yesterday. Army painter do a grey undercoat (which is the colour I've been using). As these Thunderers never see the light of day I figured it was worth a punt. Stippled Thunderers? Who cares!
They turned out great. This stuff is fantastic. I'll be using it again when my ebay order of 25 slayers arrives.