After I'm done with the final coat and before I prime, I take a cordless light and hold it against the wall and turn it sideways so that the light travels down the length of the wall. With 120 grit sandpaper in the other hand I do a once over really quickly to get any leftover imperfections.
That's the best you can get it. There's always going to be some minor imperfections no matter how good you are. Just depends on how far you want to go.
Like I said, if you drywall the ceiling, you STILL have to compound it. It's more work to drywall. Skimming the walls should not be expensive at all. A single person painter will charge a day's labor, get it done and be gone leaving the painting for you.
You can dramatically increase the drying time by mixing plaster of paris in the compound in the first and second coat. It makes the finish job stronger and more scratch proof. Though it will be more difficult to sand. The last coat should be so thin that it should dry very fast after application. I mix the compound with a little water for the last coat and use a 12" knife. An option to dry sanding the last coat is wet sanding. It's so thin that you could just take a stiff sponge, dip it, and smooth it out.
Obviously, you won't be able to skim walls to an acceptable finish without a lot of experience doing it. Have fun.