Once you do it enough times, you’ll realize that it’s easier to make it too thin and apply one more coat later than to make it too thick and have to wet sand it down. Sanding is labor intensive and annoying.
It takes getting sick and tired of sanding to truly begin to appreciate thin coats and knowing you can do another coat on top of it and not worry about laying down not enough compound…. because too thick coats and sanding sucks.
Same goes for tool marks. Once you get sick and tired of sanding, you’ll learn to be more careful with tool marks.
First time I started DIYfing mud, I thought “it’s cool, I’ll apply a bit more than I need and sand it down later, and those tool marks are cool, I’ll sand them down later”.
Now, I would rather spend time doing three more coats if I have to because I scraped too much mud off while trying to get rid of the tool marks than to leave those marks on and have to sand them.
Oh, and I bought a compressor and an orbital air sander (so that I don’t have to deal with an electric one near water when wet sanding mud) because sanding sucks. Did I mention sanding sucks?