Dave,
In the absence of local exhaust ventilation, as in a spray booth, dilution ventilation is the next best thing. I would suggest getting a good room fan going, and even opening the window, if only slightly--even in cold weather. Put the room fan behind you or slightly to the side. In an open doorway would also be good--if not best. The general idea is to force enough "fresh" air into the space that it dilutes the existing room air. The addition of a ceiling fan will help also; and don't close the registers for your HVAC system.
A respirator is a must, regardless of the paint type being sprayed in the environment you mention. I wouldn't close the door, as vapors will concentrate the longer you spray. Besides becoming a fire hazard, they'll cause your respirator cartridges' service life to expire pretty quickly. Furthermore, any solvents which may have a secondary pathway into the body through intact skin may have increased exposure potential.
The only residue to worry about should be pigment from overspray. In addition, spraying from an airbrush instead of a spray can, and acrylics instead of enamels or lacquers should reduce both the quantities and overall potential toxicities of the vapors that you have airborne at any one time.
On your airbrush, use the lowest air pressure settings you can get away with quality-wise, and schedule your painting so that you are spraying minimal amounts over minimal times--if that's possible.
Lastly, commen sense is authorized....use it and have a good time!
Hope this helps a little.
Gip Winecoff