You may also be one of the very rare people in the world who can draw a perfect circle freehand. If you are saying that you can create a flat wall with a hand trowel, you have skill which, like the circle drawing, I have never seen. You must use a plumb bob, grounds and screeds for a flat wall, the final coat is applied with a darby (up to ten foot long) or a slicker for less critical work. Then you can hand trowel in fine limeputty/marble dust/plaster pigments - just after the plaster starts to go hard. It begins to polish up as you work it. Acrylics at this stage are difficult to work because they are "gummy", sticky on the tools. Acrylics also cause a "cloudy" effect on colors, obscuring their beauty. Acrylics ARE useful as an adhesive, particularly if you are plastering over a painted wall (I will post separately on this important technique).

Don't let these tools and terms mislead you. This is not complicated or expensive, it is merely properly preparing the job and is a skill easily learned. Once learned, it will be as easy as using a compass to draw a circle. I have also found, contrary to popular wisdom, that it is your eyes that are the first thing to go as you age! I now have to trust a plumb bob for a straight line - a plasterer works by measurement, not by sight. A painter works by sight. An artist works by vision. You can wear all three hats if they fit, just make sure you know how each is separate.