Hmm. I’m honestly not sure how to answer this. I draw and paint IRL, so for me it’s like painting a bat wing on any other surface. Certainly even a line takes practice, and there are days when I’m sure my regular wing eyeliner is crooked!
If this helps you at all, I use a painting brush like this, and my eyeliner of choice for many years is MAC Fluidline in Black.
Then, I just draw the outline of how I’d like the wing to look, and fill it in.
Also I’m so glad it’s almost October so I can wear these again! I’m down for bats year-round, but you know. It’s easier to get away with this time of year.