I plan to use this in a shower over hardie backer board. Is there anything special, such as a primer etc., that needs to be done first?

Hello and thank you for your inquiry! No, the only prep required is to wipe down the cement board with a damp sponge (not wet) prior to applying the waterproof membrane; the boards are dusty. Once surface is dry you can start rolling. This product is applied in two coats. Apply the first coat in one direction and allow it to dry (typically 1- 1-1/2 hours) It changes from Miami Dolphins Blue to Jets Green when dried. Then apply the second coat in the opposite direction. When this coat dries you can install your tile with one of our polymer-modified mortars, such as Large Tile & Stone Mortar. Pre-mixed adhesives are not acceptable over Aqua Defense. If you are installing large tiles, we ask that you allow 8 hours after the second coat before tiling. Please call our Product Support line at (800) 992-6273 if you have additional questions. Have a great day! Product Advisor #9