maybe overspray landing on the surface is causing some of the roughness. What do you got for ventilation? I had a problem with that years ago when I was only using a house fan for ventilation. Doesn't move much air. But I was using basecoat so it was real easy to tack off the parts before putting on paint, since it drys so fast. Acrylic enamel singlestage your really can't tack between coats. Painting with highpressure and conventional guns, it would really get cloudy inside the garage not to mention not too healthy to be painting in (any activated paint is really bad if you are breathing it in, or its absorbing through your skin, eyes, ect) Its real easy to have a mask that has enough gaps between it in your face that you are getting exposure through that and your skin, ect. I don't know what to suggest as far as what to do about the overspray problem you are having other then to get better air movement. Also remember you need a place to take in fresh intake air opposite of your exhaust to get airflow and fresh air.
You may have to find a pattern around the car that will minimize your overspray problem. Maybe start nearest your exhaust on the first coat and painting into the airflow, and hopefully the overspray will melt in and won't be painting over rough overspray landing before you get on the first coat, and hopefully following coats it will melt in. Everyone has thier own pattern around the car and I use the same one as when I started, but overspray really isn't a problem for me anymore since I got a pretty good fan now, and have a window I can filter incoming air through on the other side of the garage. A slow activator or reducer may help with the overspray problem some by leaving the top open and wet longer. Just be carefull not to run it if its way below the temp it calls for and leave enough time between coats. You could also try hanging parts like the hood to help prevent overspray from settling on it and get it out of the stream, if you have the room. The most overspray is going to settle on the flat panels. I don't know what to suggest, maybe start another topic on avoiding overspray if no one visits this thread and has an answer for you. As far as how I spray, I normally spray a medium wet coat on my first coat with singlestage or clear. I don't worry a real lot if it isn't perfectly glossy and has a dry spot or two. The first coat I just figure as a coat for the others to stick to, and want to avoid getting runs. But still want it wet enough and free of orange peel and being rough, or you will have to try to bury it with the following coats, and that will fight you getting a nice finish. The last two I spray wetter and want it wet enough so its smooth and glossy, and on the last coat I look down and over the panel closely while painting to make sure there are no dry or missed areas and is smooth and glossy as possible without running all over the place. The last coat you want the best finish possible to cut down on the wetsanding and buffing you have to do, or in the case of singlestage metallics and pearls, as good as possible cause what you spray is what you got. Everyone has different ways of spraying. Some spray a full wet coat on all coats, Have to find what works for you. As far as time between coats, I use the times in the tech sheet as a guide, but generally wait longer if possible between coats to lessen the chance of trapping solvent or building up coats too close together. You can feel a papered off area after your first coat, and when you touch it with you finger and its tacky but not wet, (paint strings a little) your ready for another coat. This doesn't really apply to basecoat since it drys so quick, but is a guage for singlestages and clear. Sounds like you are making a little progress anyways. Hang in there you will get it eventually. Thanks to Barry K from this board, I learned black and dark colors are the slowest to dry and flash off solvents, so don't cut short your flash times. I always wondered why back when I used to have a little problem with solvent pop it was usually a black car. This forum is great, even if you have been painting for awhile can pick up things you never knew. Good luck.