Warren --
It is really pretty simple. I use a foam roller to apply the paint. As it goes on, the roller leaves a bit of very fine bubbles which is called stiple. Suppose you are painting a vertical surface like a bulkhead. You use a wide foam brush (perhaps 3 or 4 inches) and hold it very lightly in your hand. Drag it horizontally across the freshly rolled paint with the emphasis on "very lightly." It removes the roller stiple while picking up hardly any paint at all. Then when the paint sets, you have a very smooth surface. I sanded the entire hull of my Pearson Vanguard (olive drab when I bought it) and used this method with Interlux Brightside to turn it into a beautiful dark green hull. Except up close, you could not tell that it was not a spray job and I had a number of people argue with me when I said it was not sprayed. You can use the same technique with 2 part paints like Awlgrip (respirator extremely important due to isocyanate) but for me, that paint is too technical and I am not brave enough to try it as you have to get the mix just right for the conditions in which you are working. Hope that helps.
Jim