Get you some plain house fans and aim two of them IN the garage and two OUT the garage. Gotta be careful, the ones that are not sealed can spark and blow up the garage from paint fumes. Then get a LOT of light. You can try to find furnace filters, etc to filter the paint but that is not necessary since that doesn't filter too much anyways. Then for the stuff you are talking about at the end.... That is buffing and waxing the car. What you do is after wet sanding to take off orange peel, runs, etc you buff the car and then wax it... This takes out scratches from wetsanding and smoothes and shines the car up. Then the wax shines it and protects the new finish.