Rich, try setting a hotas button to "auto trim on/off toggle" when flying the K4. I have the elevator and aileron trim on a hat, the rudder on another. I don't really need anything but the elevator trim and the "auto trim on/off" while fighting in the K4. I agree, once Wep is on, having auto trim on isn't the best option, so as soon as I get into a fight, I just hit the auto trim off toggle button, and the only thing I really need at most speeds is the elevator trim, and even that is infrequent enough. When I need to, even in a fight, I can flick auto trim back on for an instant, it'll trim me out for whatever speed I'm now at, then flick it off just as quickly again, so to not have it mess up any shots I may have to take with the 30mm.
That's how I was shown to do it by Fester, and it's always worked well for me.