I did that once, so long ago that I don't know if I got all 135 slides (the 120 ones I managed to finish). It is time-consuming and after a while I started to think about my "other" photography. Becoming a good repro operator doesn't improve other photographic skills.
I don't have such a film scanner, only an Epson V750 which can take 6 stripes of film or 24 slides in one go. My approach was from the beginning, to get those files into a Mac. Which were good enough to see on which I could spend some more time or even send them to a proper scan service?
None, at the end... my current pictures are better than the ones I took on slide film during the last +30 years.
Slide film was expensive to me, so 36 frames without any other EXIF than the notes on paper are usesles to learn with. Except the Kodachomes, the colors were "interesting", but not necessarily recognizable
But the BW 120 negatives still have some nice jewels in.
I got a Kodak carousel projector, detached it's lens and changed the lamp to a 10 W version. Then I put a diffusor in front of it to equilibrate the light fall-off (but it remained and issue). At the best time, I managed to get 80 slides in less than 4 minutes to a Pentax K-m. In front of the body I mounted a Schneider componon-S which I used for the dark-room enlarger. I had to put black tape on it's aperture indicator to avoid red tinted slides. With this method I was fast and got around 9 MP/slide.
The carousel I choose because the slides are always at the same position.
I could focus a bit with a quick release rail. No, I focused by moving the projector :unsure: It was too much an effort but I could have done it fully automatically and use the time to put the slides from their standard magazines into the carousels. But after a couple of days it was done, using alternating the two remote controls. At the time we worked reduced hours, so it became possible.
Today I would not waste a single day of a weekend. It was necessary for me to do the job to come to the conclusion "my time is more valuable to work with current ideas and do them properly", but before nobody could have talked sense in me.
With the negatives, VueScan had an theoretically amazing feature: While SilverFast was doing scans for each frame separately and failed very often to detect or autocorrect them, not to mention dust removal with Infrared, the mechanics of the scanner were constantly stressed. VueScan can do RAW-images of the whole negative holder and later I used them to run single scans on the RAW scan. Quicker and less stressful for the mechanics
Unfortunately at the time it was not reliable to detect all frames. Hamrick compiled one version after another and used me as test pilot, he even wanted me to transfer 1 GB DNG (which were not recognized as DNGs from Adobe...) from my place to his office. With a DSL line, able to manage like 300 bit/s upload. He answered quickly but at some time I was pretty frustrated and he commented a moody mail from me with "I don't know what you want, I make 2 million $ per year with it, so it can't be that bad..." To be honest, the other scan apps I tried were partly horrible.