Farseer Anath'lan wrote:Yes, you can, but I would still advise painting the entire miniature.
Varnish works nicely in that it does not obscure details, and is hard to bugger up when spraying, but it doesn't provide the same level of adhesion as primer. Matt varnish works best.
Plus... it's transparent, so it's hard to tell where you've "primed". When it's the last coat, it doesn't matter, but when it's the first, you want to cover everything, and evenly.
Some people do put on a coat of varnish part way through their painting (like after basecoat), so that they can "save" their work and scrape off the stuff that goes on afterwards. Personally, I don't think it's worth the effort, because if I want to redo an area, I might as well just scrape off the area, re-prime (with Gesso) and repaint that area.