I've painted many cars in my garage. Make sure your garage is clean clean clean. Your better off using a HVLP gun, much less waste and since you already have a venting issue it will help big time. Also get a proper mask, unless you want kids with extra arms and eyes. Venting is the key also, and start on the bottom of the car first, and do the roof last , if you can tack down the roof before you paint it or you'll get alot of dirt/fallout on the roof. Also be careful of the overspray and your venting, make sure anything within 20ft of where your venting is ok to be covered in overspray, move your cars out of the driveway. It also really helps to do a dry run, plan your technique on the car without paint, adjust your technique if you find you leave a area too long, and your hose management. Have all your supplies ready to go, so you can mix paint fast, especially if your using single stage, you don't want to miss the "flash" window....you'll have fun, and you'll be "hi" from all the fumes even with a good respirator. Hope your neighbors don't complain like they did on me....