Good Morning, Bighead,
I don't know all the details of your particular camera, but I strongly suspect that your use of "Manual" mode is the correct choice. Normally, you should use the fastest possible shutter speed which will allow proper synch; with horizontally-moving focal plane shutters, that's usually 1/60, but with vertically-moving shutters, it's more likely 1/125.
Forget about metering: The autoflash feature element of the 285 is what controls the light output. Just be sure that the f-stop setting on your camera matches the "color" on the selector device on the 285. With B & W negative materials, I often use about 1/2 stop wider on the camera and slightly underdevelop the film when using autoflash; that tends to reduce the contrast somewhat; I often do the same with color negative film, since it tolerates a little overexposure better than a little underexposure.
Basic idea: just treat the camera as if it were fifty years old with absolutely no auto features. Let the flash take care of the exposure.
Konical