Soap is bad if you need to keep something lubricated but it works pretty well is you just need to lube something up a bit for installation because you can just hose it off afterwords. As far as the keycards go, that depends on the tolerance. If that tolerance is generous enough then an actual feeler gauge is overkill. A pack of keycards is dirt cheap and are all going to be about the same thickness. When one gets busted or worn then you can just grab a new one from the pack. Verses having a production guy break a feeler gauge and start guestamating because they don’t want to tell the boss they broke the third one this week.