Thanks to everyone else who posted advice here on how to steer Bugsier 2 & Ocean Star. At last it makes sense to me. Here's a trick I stumbled on by accident. Maybe it's been posted here elsewhere, but I haven't noticed it even though I read all the posts I could.
The Add-On Manual for New Horizons states: "Controlling the cruise ship with azimuth thrusters...You set the forward thrust by click-dragging the cursor up and down in the green circle. Similarly, you set the reverse thrust by click-dragging the cursor in the red circle. Lastly, you set the direction of the azimuth thruster by click-dragging the mouse left and right in the blue circle. This is best done in the bottom half of the blue circle."
IMO this is bad advice; click-dragging is difficult to do and tiring on mouse fingers and wrist. No wonder people are constructing weird & complicated azimuth controllers. Instead of looking where you should be going, you are forced to watch your mouse cursor a lot of the time.
Instead of that...
Once you've got the hang of how azimuth thrusters work, move (not drag) the mouse cursor to the heading you want the thrust to point to (inner circle zone), then click (with my slower pc I sometimes have to depress L mouse button down for half a second till it registers). The thruster will automatically swivel to where I need it. Likewise, move the mouse cursor to the outer circle zone and click to set the power. The throttle springs to the correct setting. No dragging needed, ever, and control is a lot faster.
Hope this idea helps you the way it helped me.