After you have chosen a location and time to execute your piece, you need to apply the magnet paint. If you are using the Magic Wall paint indoors, you can just apply the paint with a brush or roller. You need to paint on 2-4 coats for a reliable, robust magnetic attraction.
If you are using the paint additive and a primer sealer, you need to mix the powder additive to thick, primer/sealer paint. Follow the instructions on this site
to properly make the magnetic paint. Add 1 cup of additive per quart of paint. Remember to follow the instructions on the paint can regarding the appropriate temperature for applying the paint .