Don’t chalk your hair too often. At the end of the day, you’re using powder pigment on the ends of your hair and that can suck up a lot of natural moisture that you need in the ends of your hair.
Shampoo your hair with a clarifying shampoo after chalking. Soft chalk pastels use “gum arabic” as a binder. It’s a very very small amount and totally natural, but it’s made from a tree sap so it’s really important to get it all out.
Conditioning treatment is a MUST after you wash out your chalk. Replenish the moisture that may get sucked out with chalking.