Amsterdam Gesso is an easy to use water based primer which also helps with smoothing out surfaces like Worbla before you start painting. Simply apply apply multiple layers with a paintbrush to your cosplay armor or prop and you can dilute Gesso with water if needed to get a smoother finish.

Make sure to let each layer dry (approx. 20 minutes) before applying a new layer of Gesso. After priming you can start painting.

When priming EVA foam with Gesso, make sure you always heatseal your EVA foam first. Also note that Gesso is not really flexible when dried, meaning it is best used on solid pieces of armor and props in your cosplay.

If you are seeing brush strokes after you are finished priming, you can sand these away or apply an extra finishing layer of Gesso with a damp finger.