ᐅ curved plaster finish

Hello

Can someone tell me how to apply this "curved" plaster finish or which type of plaster is used for it?
You sometimes see this style on older houses, especially quite often on timber-framed buildings.
What kind of plaster is used for this, and is there a guide or technique for applying it?

I assume it is regular plaster that is applied in a curved way—sometimes thinner and deeper, sometimes thicker and more raised from the wall—to create this wavy pattern.

Just try searching for textured plaster; it might be helpful for you.