Well, when Dragonsreach mentioned he used Dettol to strip minis, I asked if it would work on varnished minis and he said it would. I\'m guessing simple green would also work on dullcoted minis.
For sure I stripped minis with multiple coats using turpenthine: you just need to leave them two or three days soaking in it and it will be fine. Of course they need to be metal, though: you don\'t want to use this methd on plastics...
I think Simple Green\'ll do it but try a search for Simple Green and Dullcote together and see what you find; I\'m sure one of the many threads on stripping will mention whether it\'s successful or not.
On the off chance that this doesn\'t work you could always try a two-part approach - strip off the Dullcote first, then soak in SG for the paint.
Dull Cote being more or less a clear enamel spray (Testor\'s and all...) it should slough off fairly easily with undiluted heavy-duty Simple Green. I\'ve found it works extremely well with enamel paints, moreso than with acrylics even - it ought to shift the Dull Cote just fine.
Worst case scenario: you can always put it in again for a longer soak after the first 24 hours, following a good scrub with an old toothbrush under running water to loosen things up moreso than the Simple Green\'s done by itself.
I find (inconveniently enough) that the hardest thing for Simple Green to easily shift is the old Games Workshop White Spray Primer. (Can\'t vouch for GW Black Primer as I\'d never touched the stuff...)
Is it a resin/plastic mini or metal? Simple Green for resin/plastic but for metal I love Windsor and Newton brush cleaner. It\'s fabulous on almost any paint, primer and sealer we use and I\'ve even removed 30 year old nail polish from something someone did back in the day when I...she was a bit.....um.....chemically enhanced. Works great!
I use Brakleen (disc brake cleaner) on metal minis, make sure you wear gloves, eye protection and you use it in a very very well ventilated area as it is corrosive and the fumes will make you high as a kite if inhaled too much, it DOES take dullcote off too..
I think the main point is are they metal mini\'s. As some one mentioned earlyer. Turpentine, paint thinners of nail varnish removers all work great on metal.
Leave them to soak for 24 hours then use an old toothbrush (or your girlfriends in my case lol) to scrub the left over bits of paint off.
For plastic minis I have no Idea what would shift the paint with out melting the mini\'s.