White Chalk Powder is normally used in a pounce pad to chalk stencils.  

However, Donita mixes it with Black Light Powder as follows:

• 1 part Black Light Powder  

• 3 parts White Chalk Powder

Then she puts into a little flat Tupperware container, and dips a foam paint brush into the powder.  

When she uses the foam paint brush to apply the white chalk powder to the stencil, it results in an outline that is much smoother and more even.