the way I did it was to put it on thin and even, then roll over the top different directions with just the weight of the roller doing the work to make it perfectly uniform thickness. It smoothed it so good I never had to worry about it leveling. It also made the orange peel much finer.

The first coats I did bit thicker - I was experimenting a bit. But I ended up sanding most of what I applied to get it smooth again. Then I tried different mixtures and thats when I found 50/50, 6" rollers and thin coats smoothed the way I outlined worked perfect.

This paint method is basically foolproof. Once you have the needed thickness, what makes it look so smooth is the sanding. The polishing brings out the shine - but I'm sure everybody knew that already.. lol