The fix for the misting (apart from not spraying when it's cold/humid or to excess) is olive oil. Surprising, but it works. I don';t pretend to understand why the stuff mists in the first place, but a very very thin coat of brushed olive oil will fix it (although you will need to revarnish).
I just did a complete Pike/Shotte Battalia box that had suffered that fate - see my blog for before and after shots
I have also tried many different manufacturer sprays and now have for years been using Armory's matte and primers with storage being kept inside were the temperature is controlled. With vigarous shaking before applying, when applying is completed I then remove the spray nozzle and run it through with compressed air.
The problem with using olive oil is that, within a few months, it will probably become rancid, and may also become sticky, attracting dirt. I would not trust it on any figure of mine. Who knows how it will react with the paint over time too?
Gloss varnish followed by re-matting, is a safer, tried and tested, solution.
Dullcote is fine as long as there is some sort of tough protective coating on the miniature already. This can be in the form of Gloss Varnish or the AP dips of course. Dullcote gives a figure about as much protection as a chocolate fireguard gives for a fire.
In my time I've used nearly every matt spray/liqiud on the market . My matt spray of choice used to be Humbrol but it started to get expensive for a smallish can and then inexplicably started 'frosting' and going chalky . Testor Dull Cote(which I think is expensive) is probably the best if you can get it but there were solvent issues and it was withdrawn from UK sales.I am aware it's been re released in a Euro friendly formula but have not seen the finished results. My current choice is Plasticote 'Flat' spray from B&Q,Wilko's etc. approx £6-£8 . It's a bit industrial and the spray can be fierce but once you know how to use it, the results are fine (short quick bursts from approx 20inches), a couple of coats give a robust protective coat with a good matt finish (make sure you use the tins marked 'Flat' as I've used the one marked 'Matt' and they always seems to give a slight sheen. ) Where I have got a finish with a slight sheen, I use AP anti Shine (I was given a tin from a friend) and it never fails to produce a consistent matt finish but it's only a thin coat and not as protective. I like the fine mist it produces and I spray from about 12 inches in a circular motion to envelope the model/figs in a cloud and when used over the Plasticote, it's fine, no cracking or flaking.(I only use GW paints, so don't know if other paints cause problems). Hope this is of use.