Perfect Layout can automatically (re-)create multi-measure rests in parts. It can do it both on documents where multi-measure rests have already been created and those where they have not been created at all or only partially.
The more multi-measure rests are created, the more there is a need to reflow the measures across systems.
While in music theatre scores it's common to always have a certain number of measures per line, in classical score it's more common to put more music on a line and on a page.
Perfect Layout supports these different needs by giving several measure reflow options as shown in the next images.
Image 1 is the default look before running Perfect Layout. Images 2-5 use different Perfect Layout multi-measure rest and reflow settings (from Finale's Preferences->Edit->Measure Reflow).

Image 1: A part before running Perfect Layout

Image 2: Preferences-Edit->Reflow Measures->Across Systems (Remove System Locks) activated

Image 3: MMRests->Automatic Reflow If the Number of MM Rests Has Significantls Changed activated, Preferences-Edit->Reflow Measures->Across Systems (Maintain System Locks) or Only Within Systems activated

Image 4: MMRests->Maintain System Breaks activated, Preferences-Edit->Reflow Measures->Across Systems (Maintain System Locks) or Only Within Systems activated

Image 5: MMRests->Maintain System Locks activated, Preferences-Edit->Reflow Measures->Across Systems (Maintain System Locks) or Only Within Systems activated

You can choose to apply the "Classical Look" to multi-measure rests by selecting "Force Classical Look". That means: classical rest symbols and also multi-measure rest symbols in 1-bar measures (see image 6 below). By default this option is unchecked.
If this option is unchecked, the multi-measure rest style will not be changed.


Image 6: Default Look / Classical Look

The measure number range (e.g. [24-34]) below a multi-measure rest can be very helpful for the player. But it should not include unnecessary information either. So it makes sense to not show it on every multi-measure rest, but only on the longer ones and for example after each double bar line (Option: "Show Measure Rang After Double Bar Lines").
The number of empty bars for hiding/showing measure ranges can be set twice:

a.) Absolute: "Always Hide Measure Range If Less Than X MMRest Bars". By default it's set to 3.
b.) Relative: "Hide Measure Range If Less than X Adjacent MMRest bars" also takes into account measures before and after this multi-measure rest. By default this is set to 10.
For example two multi-measure rests of 3 and 8 measures each will show the range (3+8=11), but a single 8 measure MMRest will not show the range (see image 7).

The measure range can be activated by selecting "Show Measure Number Range on MM Rests", but it currently can't be hidden if it is already visible.


Image 7: Adaptive Measure Range Visibility on Multi-Measure Rests: Visible if at least 10 adjacent measures and after double bar lines.

To faciliate reading you can select to hide tempo alterations in multi-measure rests: select "Hide Tempo Alterations in MM Rests". Depending on the content, this may be appropriate or not. This option is unchecked by default.
The sub-option "dito., But Only If No Notes Follow Until End" allows to hide tempo alterations at the end of the file if no notes follow until end. This is usually "safe" for the player.
This sub-option is activated by default.


Image 8: Some Multi-Measure Rest Settings

Right-aligned tempo marks in the last measure of a multi-measure are typically being swallowed by Finale's multi-measure rest creation algorithm.
Alternatively Finale splits the multi-measure rest and adds an extra empty measure with the tempo mark. While this may be more clear in some cases, it might be easier to read if the symbol was visible at the end of the multi-measure rest (see image 9 last line). To activate this feature select "Show Right-Aligned Tempo Marks on MMRests".
Make sure the expressions are right-aligned, attached near the end of the measure and are set to "Break MM Rest".


Image 9: Tempo Marks at the End of Multi-Measure Rests