With a turret press you buy multiple turrets, one for each set of dies you want to use. You install each set of dies in their own turret and leave 'em there permanently. The turret with its set of dies becomes a single unit that you can drop into the press quickly and easily whenever you need to switch calibers. It saves lots of time threading dies in and out, adjusting them to the right height, and fumbling with the lock rings.
The Lock n Load bushings are an attempt to bring the same convenience to single stage presses. They let you drop an individual die into the press without having to fumble with the threading and adjustments and lock rings and so forth. The LnL bushings are redundant in a turret press.
I use the Lee case trimmers. They work well enough. The case trimmer machines are probably more convenient, but I can't justify their cost.
