Hello Clem
I was afraid that would happen. Chalks need a dull surface to cling. Unfortunately they have no adhesive and can be blown off by the dullcoat. You could try over doing the color needed and letting the dullcoat almost fall on the trucks. The other option is to use "powders" like Bragdons which have adhesive included. The rubbing activates the adhesive. Don't give up with what you have, it will work with some experimentation. The colors here are a little off in the picture but you can see how the texture builds up.
Ray Marion
