Thanks for comments.
This paint is “designed” for roll and tip. The supplier specifically asked how I was going to apply the paint.
So I really hope the brush marks will not be that apparent.
As
@pclarksurf said I’m going to do the lightest brushing effort possible but it was brushing direction I was not sure of!
I watched an Epifanes rep. roll a topsides(2 part), without tipping. His technique was careful rolling - all directions - to get an even coat while keeping a very light pressure on his roller. This was the finish coat though. The undercoat was rolled on by the owner and sanded (320 #).
I prefer roll and tipping. I roll both ways with the idea of getting an even coat onto the surface. For tipping the topsides, I like to brush lightly, both ways. First, horizontally then finish with vertical strokes. I think a vertical brush mark is harder to see. But I've seen better results (from professionals) brushing either direction.
Still, this - rolling only - was an interesting technique to observe and the rep was very helpful.
All this painting is being done outdoors. That is the challenge: Weather. If you can do the work indoors, your results will be better.
The conditions for this topside were not ideal. The sun was too high, a bit of wind. This causes the coating to set before it can flow out thoroughly. If you're painting outdoors, I find the weather the most important component for a good finish.
The above results were very good. Up close, you could see the finish had a slight orange peel or roller stiple texture. In perfect conditions (cooler, higher humidity, no wind, shade), it may have flowed out more completely. But inspecting the finish this close up, you can see faint brush marks in even the best (professionally applied roll and tip) work I've seen.
Another observation I had was that this technique (rolling only) wasn't saving any time over rolling and tipping. But I learned that a light touch on the roller would probably result in a better tipping job, but it takes a bit longer to get the paint on.
The truth about a flawless finish: Once a hull is floating, the light off the waters on the topsides, gives a near flawless finish to the eye. The owner finished the above hull, himself. The rep explained the conditions and the finish that was say, ...90% of what could have been achieved in better conditions. The rep went on; if the owner wants to improve the finish, he can lightly sand next year with 320#, and give it another go.
Good advice from the rep. That's the way to look at it. Don't get too hung up on the finish that's in front of your nose while the boat is on a trailer or jack stands. This is your first attempt. Consider the challenge of getting a great finish, but leave perfection, for the next time.