What is the easiest way to paint wooden trellis? it isn't put up yet

Easiest, I think would be laying it on a tarp or drop cloth, spray painting one side, letting it dry. Flipping it over and spraying the other side. Easy!

Spray paint before you put it up.

Spray paint

Spray.

spray paint with newspaper under it...turn over after it is dry..

If you don't have a sprayer use a roller let dry flip it and roll the other side.

Then use something (cardboard box) to prop the trellis at an angle so you can spray paint the inside edges. Then prop it up in another direction so you don't miss anything. Don't forget the outside edges. This is still probably easier than brush painting. 😇

Spray paint.

spray paint, or use a paint roller