Are the grooves going to be the same color as the raised part or a contrasting color?
If it was a flat wall, then use painters tape to mark off the stripes. The grooves in the paneling changes that advice. Getting the tape into the grooves and tight to the paneling will be ever so much more time consuming.
I'd use a 2" sash brush to a steady hand on the grooves. Then use a 4" roller on the rest. Paint only one color a day.