importing scores with a variable number of staffs

Background: I sing in a choir and frequently import a score into Musescore for my personal use of the playback in order to help learn my part. I typically scan to PDF, then either let Musescore import it or let Photoscore read it. With Photoscore I correct errors and then export a music XML file. For simple choral and piano scores with a consistent number of staffs either of those processes work reasonably well. I am looking for suggestions on how to handle situations such as this example. A piece that in the printed version begins with a piano introduction, adds another staff for a part (say a soprano/alto verse) switches to a tenor/bass verse, maybe a piano only interlude, then adds back two or four vocal staffs.

As it stands now, my experimenting with importing the full piece ends up with the notes for the various parts on incorrect staffs. I am thinking the only way to accomplish what I need is to create individual PDFs, where each PDF only has a section of the piece with a fixed number of staffs. The sections would then get imported into separate Musescore files. Lastly, I would copy/paste from the sections into a blank master file with the total needed staffs. Of course, I can then use the ability to hide empty staffs to tighten things up, but it still will not fully match the appearance of the original.

My question is whether there is a simpler way to transcribe a printed score that has variations in the number of staffs. I know I can implode or expand, but AFAIK that can only happen AFTER the parts are present.