Dewey: If you only want to heat one bay of your garage to paint in, why not get two 7 foot electric baseboard heaters ( about $60 for both at Home Depot or Menards) which will warm up that section of your garage in a heartbeat and not present any problem with open flame. Also, no moving air to deposit anything on your fresh paint. My home workshop is heated that way and it works beautifully. You'd only have to use the electric heaters for a couple days, and then you'd always have them to use when you paint in the Winter. You could mount them on low stands, and they'd be portable.
BTW, can I hire you to come over and organize my shop?
No one lives forever, the trick is creating something that will.