If its got no fire bricks in it the standard 300 deg stove paint will burn straight off, try Victas 800 deg rated paint if I were you. On the other hand you can get castable refractory cement to put a firebrick lining in it. Its not expensive and is worth the extra work to achieve a stove that retains heat after the fire dies out, and not just a glowing red hot gas bottle.
I get mine from "Castree kilns " shop on eBay.
Plus remember you have to evacuate the workshop while you light a small kindling fire and cure off the paint after it has dried. It stinks and it makes you sick as a dog if you breathe the smoke.
i was pleasantly surprised with halfraud,s vht brushing paint...650 degree capable..mines has lasted nearly a year..about£6 with a trade card..and a little goes a long way..!i double skinned the door and chucked a car flywheel and some old brake discs in too retain some heat....