The general rule of the road is travel in the rightmost lane unless passing slower moving or stopped vehicles.
As a cyclist, if there's a bike lane to the right, it's the rightmost lane available to me. Just because the lane isn't available to car drivers doesn't mean I shouldn't be using it.
I take the lane when there isn't safe room to pass, sightlines from intersections/laneways are poor for cross traffic, or if the edge of the road is otherwise dangerous/too rough to travel on.
Taking the middle of the lane when there's a perfectly usable lane to your right is just like people who pull onto a freeway and take the innermost lane just to avoid worrying about traffic from onramps and offramps, even though they're going 10 or 20 below the limit. It's aggravating to other drivers, which can cause dangerous situations.
Your suggestion that you pull to the right every time a car comes up behind means you've put yourself in a situation where you have to pay EXTRA attention to what's going on behind you, even though that's really only a danger at night when riding with no lights.
Drivers of farm equipment avoid the shoulder because of the rough ride, not so that they'll get noticed.
If you're that afraid of being missed, put on some extra blinky lights.