I have been looking for a good opaque white for a while and came across great reviews for Nails Inc Floral Street.
It’s glossy in real life but the photo (or more precisely my photography skills) makes it look slightly chalky. This is three coats and no top coat. The brush was my only niggle – it was quite fat and spiked but still worked okay. I originally bought this for nail art purposes but I do quite like it as a block colour too.