Thanks for your input everyone. I won't be making the mittens, just buying them, so I can't help that they are already waterproofed. It's a gift, so I'm hopeful I can get something that will work.
I have someone who wants waterproofed leather mittens that they can draw/paint on and I'm uncertain the best supplies to get them for this task. What are some good, affordable options for creating a design on waterproofed leather mittens? Acrylic paint markers? Something else? TIA for any input!