Thought my 4 inch was fine until a big backsplash changed my mind.

Used to think that was overkill until we had a driveway pour on a 95 degree day. The ice trick kept the surface from setting up too fast, gave us time to get the broom finish right. Might look messy but it beats watching concrete crack because you rushed.

Ugh, those old doorways are the worst. I fought with a curved plaster wall for a full day once. Ended up using a flexible corner tape meant for drywall, and it finally worked. What kind of tape did you try?