It's the stuff they render houses with, it doesn't dry super smooth/flat and look like a slate tile, more the texture of a bush rock, I found it easy to apply with a $2 paintbrush ( it won't be worth keeping) if you want it super smooth you could try adding a dash of dish liquid on the final coat and use some sort of trowel to smooth it off or use tile grout instead of render on the final coat, tile gout is a lot finer than the render and gives a smoother finish. If you check out my thread "on the home stretch" you'll see the look that the acrylic render gives. Make sure you get acrylic render... The 'non' acrylic stuff takes longer to dry.
I've used bondall and Woodworking glue, and I think the bondall is better in the foam to render adhesion. Bondall is designed to helps concrete bond with concrete when patching holes and applying render to brickwork