揮灑自如

挥洒自如
huīsǎzìrú
(idiom) to do (sth) with great aplomb

CEDICT

to write or paint without constraint; to be skilful in writing, calligraphy, or painting

Wiktionary

隨意寫作詩文或書畫，不受拘束。

重編國語辭典

Entry Composition

1 揮灑 huīsǎ
  1. to sprinkle
  2. to shed (tears, blood etc)
  3. fig. free, unconstrained
  4. to write in a free style
2 自如 zìrú
  1. unobstructed
  2. unconstrained
  3. smoothly
  4. with ease
  5. freely