I could construct a proper dedicated paint room (I'm not doing that) or just wait for warm dry weather.
I'm in the same boat Pablo. I have been successful rattle can painting enamels in cold weather by:
1. Spray can heated in hot water initially and between coats
2. Whatever to be painted is in the warm house under a incandescent 100W lamp
OK, the paint and what's to be painted are warm and happy.
3. Haul butt outside and IMMEDIATELY blow on a light coat of paint (I only have to go a few steps before I can start spraying)
4. Haul butt back inside and set the item under the lamp and the paint back in the hot water
5. Repeat the above until you are happy.
Now all the argumentative theorist can say the paint will still get too cold in the split seconds it travels from the can to the item to be painted.
All I can say is I have done this successfully with enamels on butyrate and PET clear bodies and motor cans. I haven't tried it with lacquers on the outside of hard bodies.....yet.
You can test this out on a "scrapper" to see if it works for you. You are not out much if it doesn't and if it does you are back in business.