I have used the speedy’s right through a ceiling set. Put it on with a trowel neatly ( goes without saying, unless you’re a lash up artist). Plastic speedy on the pole for a gentle flatten, I rounded my corners with snips and I seldom get a line at all. Tea. Second coat. More tea. Another flatten, neaten edges with a trowel and brush. Tea. One more pass with plastic speedy. Clean up. Tea. On with the metal edged speedy, pass both ways, check edges again. Finished in time for tea.
As for pressure, you can definitely put more pressure through the pole using two arms and with both feet on the floor. But you don’t have to.