I have found a complete fudge preset on my Omni, simply back the needle of a touch, so that when the trigger is depressed, but not pulled back, you get a thin even line.
I know this undermines the whole purpose of a dual action AB, but I have found that this allows me to produce a 1/72 scale mirror wave pattern over an entire sheet of A4, with little or no variation in line width or density.
Works for me.
Karl