Gaussian Blur lets you apply an even blur to the current layer.
Prepare 2 illustrations, and add blur to one of them and Darken blend mode to create a soft-looking illustration.
Open ①Layer window , and ②Duplicate Layer , and select the ③Duplicated Layer .
Open ① the blend mode and select ② Darken.
From ① the Tool Selection window, select ② Filter.
Select ① Gaussian Blur.
Drag the ①Slider to adjust. When finished, return to the canvas with ②✓ button .
Finished.