Could one of you knowledgeable gents fill me in on bushed strikers? They are frequently listed as a feature on double guns. What is the advantage? What kind of tool is needed to change them out? I’ve read that hunters would carry spare strikers in the trap door compartments on doubles.

The bushing is accessable from the face of the breech.
A two or sometimes 3 point spanner is used to install and remove the bushing(s).
The firing pin being right behind it, so a broken or otherwise damaged pin can be removed in the field as long as you have said spanner and a replacement pin for the gun.

The firing pin being a separate part instead of being one piece with the hammer can be made to be a 'gas proof' firing pin as well.
A very good thing on a rifle.

Meaning if a primer is pierced or if the case gives out and the gas comes back through the firing pin hole into the action, the firing pin is configured so that it has a flange on it that will set back against a shoulder at the back end of it's machined cavity in the breech.
That seals off the gas from getting past the firing pin and into the area behind the action/frame.
If it travels into there it can blow out the stock wood and cause a lot of damage to the gun and shooter.

To relieve the gas that it seals off,,a bleed-off hole of a very small dia is drilled at usually a 90* angle from the FP cavity out through the fence to the outside. Usually there is a small screw head showing the location of the vent.
The slot in that screw if you look closely at it will have the vent in the center of it's slot. That's how small in dia the vent generally is and is more than good to carry the pressure away.

FYI, in lieu of a proper spanner, circlip pliers work for two hole bushings.