1) colored markers
1) Lightly draw the design you want on a sheet of paper. (Do this with straight regular lines first.)
2) Once you've finalized your design, color it with markers. trace your drawing with wiggly lines. There is no need to be neat.
Here are some of my students' artworks:
Kim Dan Bi of Grade 5-A
Koh Su Min of Grade 5-B
Mika Adarna of Grade 5-A