Hey Hey People, shadefoundry here to report the outcomes from me experimenting with spray primers.
Its been pretty well documented how Bones minis work well with Vallejo Brush-On primer, so I've been using that pretty much exclusively for them, but I only have a bottle of it in white, and that stuff is not opaque whatsoever. Since I'm slowly getting through painting my first dragon (Blightfang) I decided I'd paint up a few smaller bones minis so that I could see how they react to different things, so that I'm not experimenting on my nice dragon.
Before I get into my findings, a quick disclaimer, I did these tests with two of the light greyish colored bones, I'm not sure if things are different for the white ones, but I'll be testing with them in the near future since I have a few I'd like to get painted up for a campaign.
So, while painting my Dragoth's throne, I decided I was going to use this opportunity to play with contrast paints. Out of laziness I decided to see what would happen if I sprayed over the brush-on primer with Vallejo White Spray primer, since I didn't feel like painting on a white base coat. Now for those of you who've used that stuff before, you may have noticed that it's already a bit stickier than citadel spray primers by default, and on a Bones mini with brush-on primer it was no different. I would say that it got a bit stickier than normal, but paint adhered very well to it, and has yet to go tacky over the 2 weeks or so it's been since I finished painting it. Every day I've applied pressure with fingers to different areas to see if tackiness has come through, and so far I have yet to feel any.
My next test was with spray varnishes. This is something I've seen people talk a bit about but since I tend to use a couple of different ones in layers, I figured I'd report regardless. So I painted up an Anirion to test with, and sprayed him down with Testors Glosscote, which nobody seems to talk about. Nothing went sticky and the glossy finish didn't crack or tarnish when I bent parts of the mini. After that dried I gave it a coat of Testors Dullcote, as is my tradition with varnishing. Once again nothing's gone sticky and bending parts don't have any negative effects that I can see. This was a few days ago now, and I've been running my fingers on it and applying pressure at different parts pretty much daily to make sure nothing's gone wrong.
I'll be doing more tests this weekend once I've had a chance to pick up more Dullcote, as I've run out, but so far everything seems to be going alright.
Edit1: I had some time to test out spray priming with another mini. This time Jana, Female Dragon Slayer. Since the initial result of spray priming was a tiny bit stickier than I'd like, this time I opted to brush-on prime, followed by a very quick base coat of Scale75 Scale Color White, finished off with a spray coat of Vallejo White Spray Primer. The result was absolutely zero tack, and a very solid white coating for more Contrast Paint testing. So far this method requires the most work, but it's got pretty good results for smaller scale minis. I'll be looking into refining this process as I paint more bones minis.
Edit2: It's been like a month since I sprayed that second mini, and Jana has gone very, very tacky. I'm not sure what the difference is considering I sprayed her and Dragoth's throne with the same can of primer, and the throne is doing well. Speaking of the throne, I sprayed it down with a coat of Testor's Glosscote followed by Dullcote as I do with all my minis. Looks like Bones minis take Testors varnish no problem.
TL;DR, Vallejo White Spray Primer works pretty well if you spray a mini that's already been primed with their brush on variant, and Testors Gloss/Dullcotes have no negative effects on painted Bones from what I can tell.