I’ve used full stans kit in the past but all mine are semi ghetto now.
I just remove existing rim strip and use gorilla tape to build it up. You want it nice and tight when the tyre goes on. Proper tyer lever helps. My rims arent tubeless but I’ve not bothered with rim strips / half a tube although you may need them. I use proper tubeless valves (but cutting sone from old tubes will work), valves need to have removable cores. Add sealant (I use the stans syringe as its means when you top up the tyre stays seated). Use track pump to inflate or ghetto inflator for stubborn ones. Shake about a bit (the wheel) or ride and keep an eye on pressure over first few days. I’ve never bothered with the soapy water.
I carry a spare tube for longer rides but since going tubeless (3 yes or so) I’ve only needed it once and that was only because the tyre cut in 2 places so no chance for the holes to seal before losing air