>Handwritten notes would be easiest, but portable typewriters did exist. And libraries could have typewriters available.

Those "portable" typewriters - you might want to look up the weight & size. Then remember that "wheels on the case" wasn't a thing yet, and imagine lugging that to a public building. Also the replacement ink, erasing cartridge (if applicable) and if it's electric you're gonna need to plug it in.

Notes were easier - we were there.

>I am slightly too young to remember what kind of copy technology my library had in the mid-1980s, but commercial copiers were introduced in 1959, so it's entirely possible that libraries has them.

Largely, they did not until the 90s.