Asi

the worst nightmare was installing rubber springs onto pawls (an odd spring to use, a block of rubber that is attached to the pawl on a Regina FW, 3pawls, 3such springs that are not held by anything but the fact that it cannot slip out once the pawls and the ramps on the gear body is installed)

Another nasty thing is to install individual steel springs like a safety pin (that is looped around into a recess of the fixed part and a recess hole on the back of the pawl) - it must be installed at once (the pawl and the spring) - in a XB3 hub/fw combo (since the fixed part of the FW it is cast with the hub itself, not removable, when the ratchet mechanism is toast, the hub is toast)

There are some times, lamellar individual springs that are usualy not removable since they are being clamped by force into a small slot into the fixed part (and since the spring is not removable or at least not installable again, the pawls cannot be removed) - in a maillard FW (non-helicomatic)

In shimano silent FW/hub you will find lots of rollers and lots of springs inside. That is a badass to put in again (it does not have pawls but lots of rollers that wedge themselves onto ramps in one way of turning and slip in the other way)

In a single speed freewheel i had found a coiled band that it was tight to the hub when coasting and it would unwind and expand and stick to the exterior housing (the gears part) like a drum brake. (on a "Ukraina" utility bike)

Most newer FW have 2-3 pawls held by a ring spring, which is pretty convenient to dissemble/reassemble. (use some grease to hold the balls in the raceway, and some tweezers to manipulate the small balls)

On the bottom line: if the FW do not have play side to side, the mechanism works (it does not slip in forward resulting in free pedaling, and it does not stick when back pedaling) then do not dissemble the unit.