/diy/ - Do It Yourself

so /diy/ I'm in a bit of a pickle
I got my hands on a fairly large amount of vintage typewriters for next to nothing and while some work perfectly out of the box some require maintenance and tune up. I want to restore them all and keep some flip some but I can't find much outside most general information on the proper maintenance proceedings and fixing stuff and I would be most happy to avoid taking first two apart just to learn the in and outs for what mostly will come down to to replacing a spring or a string.
Do you happen to know of / have any documents pertaining to this subject?
I learned through google that reader's digest repair manual "the complete guide to home maintenance" and "complete do-it-yourself manual" are supposed to have some sections on typewriters but google results for those are some clickjacking sites.

Any help and advice will be appreciated. Machines are mostly 70s and 80s polish Łucznik/Predom commie machines but they are based on Singer and Facit licences.
This site has some info but the designs often differ significantly https://typewriterdatabase.com/manuals.php